Britain's actions on the world stage must "match our values and our words", the new chairman of the Commons Foreign Affairs Select Committee has said.
Tory MP Tom Tugendhat said too often the Government had defended foreign policy decisions with mediocre arguments.
Speaking at a fringe event at the Tory conference in Manchester, Mr Tugendhat said many major foreign affairs issues were used to "signal something which is simply not true".
He added: "That's where we've got to be honest.
"I think there is a room in politics for honesty, I think there is certainly a value in it and I think there's a strength to it.
"Too often, the way we have justified, and this is a problem with conservatism, the way we have discussed and defended our foreign policy actions has been 'oh, because it creates jobs in whichever constituency it happens to be', or because you've got to understand if we didn't sell x product, then somebody else would.
"Well, that is an argument, but it isn't the key argument.
"We are a powerful country, and a rich country, with alliances around the world, and we must make sure that our actions match our values and our words.
"Sometimes that will lead to uncomfortable decisions, with difficult conversations with ambassadors and heads of state from around the place, but actually it would make us stronger and more prosperous if it's seen that to be an ally of the United Kingdom is a good place to be."