Parliament's biggest pro-Israel lobby group has attacked the British ambassador to the country after he claimed that public opinion was turning against Israel due to its policies on settlements and treatment of Palestinians.

Conservative Friends of Israel said Matthew Gould's remarks on anti-Israel sentiment in Britain and boycott campaigns were "unrepresentative of reality".

Mr Gould voiced his concerns on Israeli television, saying those worried about Israel's standing in the world "should be concerned about the erosion of popular support" for it in Britain.

Israel was now increasingly seen as the "Goliath" and the Palestinians as "David", he said.

The changing perception was not among "these people on the fringe who are shouting loudly and calling for boycotts and all the rest of it. The interesting category are those members of parliament in the middle, the majority, and in that group I see a shift," said Mr Gould. "The problem is not hasbara. The centre ground, the majority, the British public may not be expert but they are not stupid, and they see a stream of announcements about new building in settlements, they read stories about what's going on in the West Bank, they read about the restrictions in Gaza. The substance of what's going on is really what's driving this."

CFI director Stuart Polak said the comments did not reflect the actions of Tory MPs. "Conservative MPs 'in the middle' of the debate are very engaged and regularly make their voices heard in support of Israel on a wide range of issues," he said.

"Most recently, for example, MPs have been active in raising the matter of Palestinian incitement, an area they believe the government ought to examine more closely."

Mr Gould also warned: "Israelis might wake up in 10 years' time and suddenly find that the level of understanding in the international community has changed; that the level of patience for continuing the status quo has reduced."

Israel's Minister for Sport and Culture, Limor Livnat, said it was "very unusual for an ambassador to say such things. This is the British attitude towards the settlements for years and years, nothing is new. On the contrary, Israel now builds less settlements than in the past.

"About the suggestion that less and less MPs support Israel, I don't think it's true. I am in touch with British Jews and I don't know what he's talking about. I think it's very dangerous to make such statements, and it is not what I would expect of a diplomat. Matthew Gould is a very nice person, I meet him from time to time. But I think [his remarks] were a kind of exaggeration."

The comments brought a mixed reaction from British groups supporting Israel. Board of Deputies chief executive Jon Benjamin said: "It would be rash to deny that perceptions of Israel are frequently negative.

"Some of those now taking issue with the ambassador's comments are the same people who decry the treatment of Israel in the British media. Certainly elements of the media have much to answer for, casting every story about Israel against a backdrop of supposed intransigence from Israeli governments, and saying little or nothing of the wilful refusal of Palestinian leaders to engage with the peace process.

"Without setting Israel's actions in context, whether or not the average Briton agrees with them, the level of misunderstanding and misinterpretation of those actions will only deepen."

Dermot Kehoe, Bicom chief executive, said the relationship between Britain and Israel had "never been stronger in terms of trade, technology and security co-operation. Our polling shows the relationship is not eroding.

"The ambassador is right to highlight the importance of the peace process to the British public. However, Israel is not Goliath. It is a small country surrounded by threats from Iran to Hizbollah to Hamas. Palestinians also share responsibilities to return to the negotiating table in the search for a lasting peace."

Gavin Stollar, LibDem Friends of Israel chairman, said: "Mr Gould is a distinguished diplomat and while I wouldn't agree 100 per cent with his comments, he should feel free to reflect opinion as he sees it."

However, an Israeli Foreign Ministry source said privately that it was a pity more diplomats did not say what Mr Gould had said.