Conservative MPs have been urged to rally around their leader as he returns from the Tory's latest initiative in Rwanda.
As a whispering campaign against David Cameron spreads across the Tory backbenches, David Davis urged MPs to "show a bit of discipline".
After Brown-ally Ed Balls said Mr Cameron had suffered his "worst week yet", Mr Davis admitted the party was going through a "slightly difficult phase".
But he insisted he backed Mr Cameron and said the party leader had "passed his first test".
Mr Davis said: "I think the real truth is we are going through a slightly difficult phase when we have the 'Brown bounce'.
"My argument to my own party is that David Cameron has passed his first test, it's now time to show a bit of discipline and pass yours."
Mr Davis struck a fine line between supporting his former rival and stamping his own authority on the party.
The shadow home secretary's motivations were further blurred after it emerged he is heading towards a power struggle with the shadow justice secretary Nick Herbert.
Mr Cameron is expected to meet with the two frontbenchers tonight as the shadow ministers wrangle over responsibility for prisons - increasingly become a prominent political battleground.
Party insiders told the Times the row marks a deteriorating relationship between Mr Cameron and his home secretary.
Mr Cameron also faces the threat of rebellion from his backbenchers. Right-wing Tory MPs are said to be increasingly prepared to challenge Conservative policy.
Lord Kalms, the former Tory treasurer and Davis-backer, said Cameron was facing a "summer of discontent" and ought to "do some rethinking".
The party has suffered from infighting over Mr Cameron's stance on grammar schools, taxation and energy policy.
The Tory leader failed to win a much needed validation for his modernising agenda, after the party - specifically branded as David Cameron's Conservatives - were pushed into third place in recent by-elections.
An ICM/Guardian opinion poll confirmed Mr Cameron is failing to attract new voters to the Conservatives, while alienating the party's traditional supporters.
Mr Cameron conceded the by-election results could have been better, but said it was time to move "on to the next test".
Unfortunately for the Tory leader, this took him to Rwanda at the same time as his Witney constituency was hit by flooding.
Mr Cameron was embarrassed when asked on Rwandan television why he had not returned to the waterlogged UK.
He was also heckled during prime minister's question time for his absence; with Gordon Brown and Ming Campbell both able to boast of their own visits to flooded areas.
Commentators agreed Mr Cameron had won the first rounds in the Commons against Mr Brown's "clunking fist". However, today the prime minister delivered a stinging rebuke to the embattled Tory leader.
Mr Brown accused Mr Cameron off retreating to the old Tory agenda on grammar schools, Europe, taxation and more.
"The wheels are going off the Tory bicycle and it's just as well he's got a car following him," he said.
Commentators now suggest Mr Cameron's team fatally underestimated Mr Brown's seriousness as a politician and are now shaken by the so-called "Brown bounce".