Nick Clegg has accused Israel of damaging the peace process, calling the country's expansion of settlements in Palestinian territories "an act of deliberate vandalism".
The deputy prime minister made the outspoken remarks during a joint press conference with Palestinian president Mahmoud Abbas.
"Once you've placed physical facts on the ground that make it impossible to deliver something that everyone has for years agreed is the ultimate destination," he said
"It is an act of deliberate vandalism to the basic premise on which negotiations have taken place for years and years and years. And that is why we have expressed our concerns as a government."
Clive Jones, a professor of Middle East studies at Leeds university said the comments were "more outspoken" on the issue than previous remarks by British politicians.
"William Hague tends to restrict himself to comments like 'unhelpful'. Nick Clegg's probably gone further than many British politicians who hold government office," he told Huff Post UK.
David Cameron has raised the issue of settlements in his New Year's phonecall with Israeli prime minister Benjamin Netanyahu.
A Downing Street spokesperson said the prime minister had "raised concerns" about Israeli settlements in the West Bank and East Jerusalem.
"He said such settlements were illegal, and that announcements of further building in them were doing real damage both to Israel's reputation and to prospects for peace."
Professor Jones said the subtext to the issue was the West seeking to gain consensus over sanctions against Iran: "Many European leaders would say building settlements is unhelpful in trying to create a consensus in Arab opinion over the need for strict sanctions on Iran. The subtext of this is to stop the spread of the proliferation across the Middle East, if that it is indeed what the Iranians are trying to do."
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