Foreign Office minister Sir Alan Duncan has pledged to get tough and not be "mealy-mouthed" with Turkey, which has threatened to bring back the death penalty for plotters behind the failed coup.
Turkish president Recep Tayyip Erdogan has ordered the arrest of 6,000 members of the judicial and military, while 8,000 police officers have been suspended following the failed putsch.
British MPs raised concerns that president Erdogan is using the failed coup as a "blank cheque" to round up his opponents, and urged the Government to get tough with the ruler.
Responding to questions following an urgent statement on the issue to the Commons, Sir Alan said he would make it clear to officials when he flies out to Ankara on Wednesday that human rights and the rule of law must be upheld.
Sir Alan, who was standing in for Foreign Secretary Boris Johnson, told MPs: "When I am in Ankara tomorrow I will not be mealy-mouthed in saying what we think needs to happen, and human rights, not reintroducing the death penalty, and the proper due process of law, will of course from a very large part of what we would urge upon the Government of Turkey."
He strongly condemned any proposed moves to reintroduce the death penalty in Turkey and echoed remarks made by the German government that Turkey would not be able to join in the EU if it did readopt executions.
Sir Alan said: "It is very strongly the view of Her Majesty's Government that we oppose the death penalty. It is also the view of all like-minded governments.
"It would be a deeply retrograde step, which I think would cause incalculable damage to the standing of Turkey just at time when it is important to embrace them within the world community and not see them become more isolated form it."
He added: "I believe I'm right in saying that if Turkey were to reintroduce the death penalty it would be disqualifying itself from membership, or future membership, of the EU.
"So in that sense it would be a self-defeating act, and against the objective of potentially them joining the EU."
Members of Turkey's military attempted to stage a coup on Friday night, but they were repelled after President Erdogan appealed to his supporters to take to the streets to save the regime in a Facetime interview with a television network.
Some believe he is using the plot as an excuse to round up his opponents and stamp out dissent among the military and civil service.
Under President Erdogan the Turkish government has been accused of being increasingly authoritarian - cracking down on Kurds and undermining press freedom by seizing control of newspapers and press agencies.
SNP MP Alex Salmond said: "While no responsible government can support a military coup against a democratic government, no responsible democratic government engages in the suppression of civil liberties, the persecution of minority communities like the Kurds, the imprisonment of thousands of people, the suspension of Parliamentary rights, the reintroduction of the death penalty."
He urged the minister to "make it clear to President Erdogan, it is not just European Union membership that's at risk from that course of action, but Nato membership as well".
Former justice secretary Michael Gove also urged Sir Alan to highlight the importance of democratic and human rights.
He said: "Will you take this opportunity to ensure that president Erdogan and his allies appreciate that press freedom and freedom of speech is one of the values that those behind this coup want to crush, and which he should seek to uphold?"
Sir Alan replied: "He is absolutely right that freedom of speech, freedom of the media are absolutely essential to the proper working of any democracy and indeed any country."
But he stressed that he hopes Turkey will "remain a full and compliant member of Nato".
The minister said he is not aware of any UK citizens arrested during Friday's clashes, which MPs heard has killed more than 200 people with some 1,400 injured.
New Foreign Secretary Boris Johnson was not in the Commons chamber for the urgent question about the failed coup in Turkey.
Some Labour MPs shouted "Where is he?" as Sir Alan replied to shadow foreign secretary Emily Thornberry on behalf of the Government.
Tory frontbencher Sir Alan said of the deaths and injuries caused by the military uprising: "I'm sure the whole House will join me in expressing our sympathies and condolences to the people of Turkey on this tragic loss of life."
Sir Alan also shed further light on Prime Minister Theresa May's conversation with president Erdogan, which took place on Monday night.
He said Mrs May "commended the bravery" of the Turkish people, adding: "The Prime Minister underlined our support for Turkey's government and democratic institutions, stressing there was no place for the military in politics.
"The Prime Minister underlined the importance of our cooperation on counter-terrorism, migration, regional security and defence."
Sir Alan turned to the response of Mr Johnson, including taking part in the EU Foreign Affairs Council, and said: "There's a strong sense of common purpose between us and our European partners.
"The Foreign Affairs Council has issued conclusions strongly condemning the coup attempt, welcoming the common position of the political parties in support of Turkey's democracy and stressing the importance for the rule of law prevailing and its rejection of the death penalty.
"The Turkish government now has the opportunity to build on the strong domestic support they gathered in response to the coup attempt.
"A measured and careful response will sustain the unity of purpose which we've seen so far and which was so clearly evident on the streets of Istanbul and Ankara."
Sir Alan said the UK "stands ready" to assist Turkey with its reforms and help the democratically-elected government "restore order in a way that reflects and supports the rule of law".
Ms Thornberry questioned if UK officials were surprised by the coup, also telling MPs that 500,000 people of Turkish and Kurdish descent live in the UK and are "desperately worried" about their families.
She added: "With two million visitors a year, Turkey is greatly loved in this country and the interests of our two countries can't be separated."
Ms Thornberry questioned how many Britons were arrested as a result of the coup and asked for advice for travellers heading to Turkey.
She said the early signs of whether president Erdogan will undermine or strengthen democracy were "deeply worrying".
Ms Thornberry later asked: "Was the Foreign Office taken by surprise by this attempted coup?"
She also questioned what will happen to the UK's "vital ally".
Sir Alan replied: "I'm not aware of any UK citizens who have been arrested but that is a very serious consular objective and for us to pursue and find out and make sure that that remains the case."
He said the due process of law should be upheld, any trials should be "fair", and the "highest principles of democratic standards" should be upheld.
Sir Alan also said to Ms Thornberry: "I very much hope in the reaction they display to this coup attempt that Turkey will be able to remain a very important member of Nato and a partner to other countries within Europe.
"In answer to your very straightforward question about whether we were taken by surprise - yes. I'm not sure there was anybody who wasn't."