Stewart Jackson, said immigration was challenging the economy as voters' top concern, and the Prime Minister had to be "bold".
The Peterborough MP's comments in an article for the ConservativeHome.com website, follow the surprise defection of Tory colleague Douglas Carswell to Ukip last week.
The move has put the premier under renewed pressure to adopt a harder line on Europe - including stating that he could campaign for a British exit in the referendum mooted for 2017.
Mr Jackson insisted the departure of Mr Carswell should act as an "impetus and imperative to articulate a clearer and compelling and deliverable vision of a pre-referendum relationship with the EU".
He warned that Ukip was "feeding off real and imagined fears" about immigration, and Mr Cameron had to be strong on the issue to remain Prime Minister
"Cameron must be bold on this issue, if he is to win back the voters' trust and a sizeable chunk of Ukip voters, most of whom couldn't give a monkey's uncle about the EU but are angry about unrestricted immigration and its impact," Mr Jackson wrote.
"That means effectively ripping up the Free Movement Directive, adopting the tough German and Spanish models on social assistance and public services for migrants and challenging the European Court of Justice.
"It means suspending our membership of the European Court of Human Rights - as Sweden once did - and it means a huge boost in funding for UK Borders.
"Fundamentally, platitudinous flim-flam about repatriating powers (unspecified) from the EU just won't cut it any longer."