Foreign Secretary Philip Hammond is facing fresh calls from MPs to make a Commons statement on the possible deployment of British ground troops to Libya.
The cross-party Commons Foreign Affairs Committee has angrily rejected Mr Hammond's latest "less-than-candid" assurances that no deployment to the strife-torn north African state is imminent.
The row follows a visit by MPs to Egypt and Tunisia last month during which they said they were told the UK was to contribute 1,000 troops to a 6,000-strong international force to be despatched to support a new UN-backed government of national unity "in the near future".
In their latest exchange of correspondence, released by the committee, Mr Hammond said no decisions had been made about any future British deployment.
"I have taken the precaution of checking with our embassies in Cairo and Tunis. They have confirmed that at no point did British diplomats brief you to this effect. Your assertions are wrong on a number of accounts," he wrote.
That drew a furious response from the committee chairman, Conservative former minister Crispin Blunt, who said his letter was designed to be "wholly and deliberately misleading to the uninformed reader".
"As you are no doubt aware given your careful choice of words, the briefing came from another British source working at the direction of the defence attache and witnessed by British diplomats," he wrote.
He added: "The Foreign Affairs Committee remains deeply concerned by potential British military involvement in Libya.
"The welcome candour of briefings by all whom we met in Cairo and Tunis contrasts sharply with your less-than-candid reply to my request for further detail on a rapidly developing situation that may require further active British engagement."
He called on Mr Hammond to make a statement to the Commons "clarifying" the UK's current military involvement in Libya and its plans to deploy troops to the country.
A Foreign Office spokesman said there are no plans to deploy combat troops.
"As the Foreign Secretary has made clear, the UK continues to work with international partners on how to best support the new Libyan government. This includes discussions about a Libyan International Assistance Mission.
"The Foreign Secretary has also been consistently clear that while no decisions have yet been taken, there are no plans to deploy combat troops and that planning has been focused on training Libyan security forces to provide their own security," the spokesman said.