David Cameron is "not looking very likely" to secure a good enough reform deal to justify keeping Britain in the European Union, former Tory leader Lord Howard said.
The peer delivered a pessimistic assessment of his successor's chances as the Prime Minister travelled to Prague on the latest leg of his diplomatic offensive ahead of next month's crunch summit on his demands for European Union reforms.
Mr Cameron will hold talks with his counterpart president Milos Zeman and Bohuslav Sobotka in the Czech capital in an effort to win support for his reforms, including the thorny issue of action to curb EU migration.
He has insisted he is in "no hurry" to secure a deal on a package of changes to Britain's EU membership at the upcoming Brussels summit in February but if a suitable agreement is reached he will "sell it very hard" to the public ahead of the promised in/out referendum.
A deal at the European Council of February 18-19 is widely seen as essential if Mr Cameron is to stage the plebiscite before the summer.
But Lord Howard made clear he would be surprised if any deal was sufficient to convince him to back continued membership.
"I am waiting to see what the Prime Minister is coming up with.
"I have always wanted the United Kingdom to remain in a genuinely reformed European Union," he told BBC Radio 4's Today.
"It is not looking very likely I have to say that we are going to see a genuinely-reformed European Union.
"We will have to wait and see. I have great respect and admiration for the Prime Minister. He may surprise us; he has been rather good at surprising us in the past."
The peer said he had "a lot of sympathy" with the view expressed by Michael Caine in an interview with the programme, in which he said Britain should leave the EU unless there were "extremely significant" reforms.
The veteran actor said the consequences of a so-called Brexit were "scary" but so were those of being "dictated to by thousands of faceless civil servants".
"I sort of feel certain we should come out," he concluded.
Lord Howard said: "I have a lot of sympathy with what he said but I am prepared to wait and see what the final deal looks like and then I'll decide."
Mr Cameron's proposal for a four-year ban on migrants claiming in-work benefits in the UK has become the main stumbling block, with the Government prepared to consider other options if they meet the aim of curbing the numbers coming from other member states.
The UK has been working to persuade members of the Visegrad Group - the Czech Republic, Slovakia, Poland and Hungary - to support the plans.
In December the group issued a joint statement saying they would back measures aimed at strengthening competitiveness and increasing the role of national parliaments but they "consider free movement one of the fundamental values of the European Union and will support no proposal that would be discriminatory or restrictive with regard to this freedom".