Christians for EU spoke to the News Hour as the Prime Minister joins other leaders from the bloc for a crucial meeting in Brussels.
An agreement on his plans could pave the way for an in/out referendum on the UK's European Union membership as soon as June.
The Very Revd Michael Sadgrove, a former Dean of Durham Cathedral and founder of the Christians for EU group said: "[David Cameron] has to win hearts and minds as we've always said. I think he needs to talk-up the Union for all the possibilities it offers, for the benefits that we all derive from living on a continent as a common European home.
"I am very concerned that we might lose this referendum, just as I was concerned in 2014 that we might lose the Scottish referendum on independence.
"I just don't think that these are necessary votes to have when there are so many crisis facing our nation, and indeed the continent and the world.
"We're distracting the whole of Europe from dealing with refugees and other crisis that are facing Europe in order to concentrate on Britain's particular needs.
"I just don't think that this is all-together helpful, however, given that we are where we are, I am hoping the Prime Minister can pull it off."
Arriving in Brussels earlier, David Cameron said he was "battling for Britain" as the summit, which is being billed by the European Council president Donald Tusk as a "make-or-break" moment.
Mr Cameron insisted he was not in a rush to secure an agreement at any cost.
He said: "We have got some important work to do today and tomorrow and it's going to be hard. I will be battling for Britain; if we can get a good deal I will take that deal but I will not take a deal that does not meet what we need.
"I think it is much more important to get this right than to do anything in a rush. But with goodwill, with hard work, we can get a better deal for Britain."
Key elements of the Prime Minister's proposed changes still have not been agreed upon and will be decided in the meeting in Brussels.
UKIP leader Mr Farage said: "[David Cameron] hasn't asked for us to get back supremacy for our Parliament, he hasn't asked for us to control our own borders, he hasn't asked to reduce the vast daily fees we pay.
"We will be allowed - after he has come here like Oliver Twist and begged for concessions - to control migrant benefits for up to four years. I find the whole thing as a British person pretty shameful.
"And the worst bit is that whatever he comes back with and tries to sell to the British people is not legally binding. It can be struck down by the European Parliament and ultimately all of it can be ruled out of order by the European Court of Justice."