David Cameron insisted today he was "even more committed" to the coalition than he was when it was formed two years ago.
The Prime Minister admitted questions had been raised about the future of the partnership between the Conservatives and Liberal Democrats in the wake of the Tory rebellion last week over House of Lords reform.
But he insisted there was a "huge momentum" in the Government to rebalance the economy and education reforms.
He said: "I just want to say I am even more committed to coalition government, to making this coalition government, today than I was in May 2010 when Nick Clegg and I formed this government.
"I believe it has real purpose, a real mission."
Mr Cameron was speaking on a joint visit to Birmingham with Deputy Prime Minister Nick Clegg, where they announced a £9.4bn investment in the electrification of Britain's railways,
Mr Clegg dismissed the Lords row as one of the "bumps in the road" to be expected in the circumstances, especially on an issue which excited strong opinions among politicians.
But despite disagreements between the two parties, he added: "None of that will stop us from continuing to govern in the national interest for the country."