Ex-shadow transport secretary Damian Green says he refused a new Tory front bench job so he could argue the case for "compassionate Conservatism".
Green says the party must seek broad support
Mr Green left during last week's Tory reshuffle which saw John Redwood's return to the shadow cabinet.
Mr Green told the BBC he had turned down a swap to a constitutional affairs brief as he wanted the "freedom of the back benches" to argue his case.
The MP warned the Tories against trying to appeal only to its core voters.
Michael Howard's critics have portrayed the reshuffle as a "lurch to the right".
As well as Mr Green, modernisers John Bercow and Julie Kirkbride left the front bench after refusing other jobs.
Ashford MP Mr Green told BBC Radio 4's Today programme: "I want to argue for a form of
compassionate Conservatism, the sort of Conservatism that was very effective for
George Bush a few years ago.
"The freedom of the back benches allows me to do that, because I think that's
the way the Conservative Party will get back to power.
Redwood's return as been attacked as a move to the right
"Individuals don't matter very much in reshuffles. Any politician is
replaceable at any time.
"What matters is the overall tone and I'm worried - I
would be worried - if we went back to the so-called core vote strategy."
Such a shift would involve focusing on issues such as Europe and asylum, he said.
"We tried that at the last election and we have seen what happened. It
doesn't work," argued Mr Green.
Spending time facing up to the threat posed by the UK Independence Party would lose voters at the other end of the political spectrum, he warned.
Mr Green insisted he was "delighted" by the return of right-wing former Welsh Secretary Mr Redwood.
"I'm a fan of John
Redwood, he's a very good politician," he said.
"It's the overall tone I want to see got right. We need a balanced