David Cameron is coming under fierce criticism from centre-right allies in Europe for his decision to ditch mainstream ­conservatism in the EU in order to lead a new movement of Eurosceptics.

In advance of next month's European elections, the Tory leader came under fire from senior figures over his move to end 17 years of alliance with the European ­People's party (EPP), which groups the centre-right in the parliament, and to establish a caucus of "European Conservatives". In separate developments:

* Chancellor Angela Merkel of Germany appeared to threaten to withhold cooperation from the Conservatives.

* Cameron's close ally, Fredrik Reinfeldt, the Swedish prime minister, warned the Tory leader that he faced isolation. ­Reinfeldt called on Cameron to reverse his decision to quit the EPP.

* A senior Czech politician added that his liberal rightwing ODS party, a key ­Cameron partner, was having second thoughts about joining the Tories in the new caucus being plotted.

* Hans-Gert Poettering, the German Christian Democrat who presides over the European parliament, angrily described Cameron as untrustworthy.