Ashton predecessors urge firm line on Israel

They noted that Palestinians resumed the talks, in part, because the EU rules gave them confidence.

"Their strict application serves to re-iterate that the EU does not recognise and will not support settlements and other illegal facts on the ground … which threaten to make a negotiated solution to the Israeli-Palestinian conflict impossible," the letter says.

"A delay or suspension of the guidelines ... would undermine the negotiations by alienating the Palestinians and by reinforcing Israel’s intransigence," it notes.

"It would [also] damage the EU’s credibility and erode its vital foundations as a law-based community," it adds.

Signatories include four former EU foreign relations chiefs: Javier Solana, Benita Ferrero-Waldner, Hans van den Broek and Frans Andriessen.

They also include Miguel Moratinos, a former Spanish foreign minister and EU special envoy on the peace process.

Former Dutch and Irish leaders, Andreas Van Agt and John Bruton, former French foreign minister, Hubert Vedrine, and former Portuguese foreign minister, Teresa Patricio Gouveia, signed the letter as well.

The EU in July published guidelines which force Israeli institutions and firms to sign contracts pledging not to use EU money to fund activity on Palestinian land.

Israel has given up on trying to get the rules deleted.

But it says it will not join EU projects, such as the Horizon 2020 science scheme, unless the Union drafts agreements which do not force it to acknowledge EU-and-UN-recognised borders.

Talks on Horizon 2020 in Brussels last week ended without a solution.

But the European Commission said the two sides identified "options" which might make it easier for Israel to swallow the new funding regime.

This article was altered at 12.20pm Brussels time on 16 September after three more signatories joined the original 12 names