The sacked Liberal Democrat minister Jeremy Browne has claimed his party is like a shopping trolley that has veered to the left, and urged party colleagues to stop talking about the things they have prevented the Conservatives from doing and instead focus on the coalition's achievements.

Browne, who is on the right of the party and had been seen as a rising star, admitted he had been pained and puzzled by his dismissal in the ministerial reshuffle.

The Liberal Democrat leadership had become exasperated by what they regarded as his challenges to party strategy, as well as aspects of his performance in the Home Office. Party leaders had wanted him to take a more independent line from the home secretary, Theresa May.

Browne hit back in an interview in the Times, saying a "substantial number" of his colleagues appeared to be happy for the Lib Dems to be considered a "peripheral force that campaigns against the Conservatives".

He confirmed weekend reports that he had been approached by the Conservative party chairman Grant Shapps to defect from the Liberal Democrats, but had rejected the approach. He said he had even turned down a meeting.

Senior Tories believe he may yet shift in what is a highly marginal seat, but possibly not until closer to the election as the fissures between himself and his party leadership become wider.

Comparing the Lib Dems to a shopping trolley that "left to its own devices defaults to the left and to being the party of protest", Browne said he became exposed after years of trying to exert "corrective pressure".

"I saw my role, and continue to do so, as doing everything I can to accelerate the Lib Dems' journey from a party of protest to a party of government," he said.

"If the Lib Dems look ambivalent about being in government we can hardly then complain if people assume that its successes must be down to the party that doesn't look ambivalent. You can't be half in and half out of government. We have to avoid the trap of looking like a party that is a reluctant party of government and looking uncomfortable and that we'd be grateful to be relieved of our collective responsibilities.

"There is a role in politics for stopping things you don't want to happen, but I want the greatest emphasis to be on what we have managed to achieve rather than what we have managed to prevent the Conservatives from achieving. We will stand at the next election with our own policy offer but that doesn't mean that we should disengage from the central pillars of the government; we should co-own the central propositions of the government."

To those who say he's in the wrong party, Browne said: "I'd turn that on its head. I'd say my ambition for the Lib Dems is to attract the small 'l' liberals in the Conservative and Labour parties. I regard it as a disappointment that we have not attracted more people of a liberal disposition in other political parties."

He says his dismissal was disorientating, and suggested he was given a black mark for failing to stop the home secretary's plan to send vans around London telling immigrants to go home. Browne said he was not copied in on the correspondence, but it appears that a special adviser was.

Some senior Lib Dems claim he had not been effective in the Home Office, and allies of the business secretary, Vince Cable, said he may have briefed against him in a way that in turn led to instability at the party conference in Glasgow.

Browne was eager to stress his grassroots credentials, saying: "Not many people have delivered more leaflets than me or knocked on more doors than me or helped in more council byelections than me."