Energy Secretary Ed Davey said the Tories and Liberal Democrats were parties with different values and histories.
But he defended the coalition in the wake of this week's Conservative rebellion on Lords reform - and insisted the plans were not dead.
He told the Sky News Murnaghan programme:
People are forgetting that we had a historic vote in the Commons just recently when a huge majority voted in favour of the principle of a democratically elected House of Lords.
That has not happened before. I also believe it is part of the Coalition Agreement and the Conservative Party will want to honour their agreement and I'm delighted the Prime Minister said he's going to have another go.
David Cameron has issued an appeal to warring Tories and Liberal Democrats to unite behind the coalition not descend into "division and navel-gazing".
Following last week's Conservative revolt over Nick Clegg's plans for House of Lords reform, the Prime Minister frankly acknowledged there were "profound areas of disagreement" between the two parties.
But in a letter to The Sunday Times, he said it was essential that these differences did not stop them working together in government.
"These differences matter and at the next election they will help define us. But we're not in an election, now. We're not even close," he said.