DAVID Cameron finally delivered on a four-year-old pledge to establish a new centre-right grouping in the European parliament when the Tories announced they would lead a 55-strong bloc of social conservatives in Strasbourg and Brussels.

Labour accused the Tories of moving to the extremes of Europe after the party confirmed that its 26 MEPs would sit with Poland's homophobic Law and Justice party among others on the right.

The launch of the new movement means Cameron has abandoned two decades of Tories being in the mainstream of European politics for a new alliance on the rightwing fringes.

When the new parliament meets for the first time on July 14 the Tories will sit in a new block, known as the European Conservatives and Reformists. This fulfils a pledge by Cameron during the 2005 Conservative leadership contest to leave the EPP-ED group in Strasbourg, the largest group, with members from the main centre right parties across the EU.

While the EPP centre-right mainstream encompasses governing parties in half the EU, the new grouping is almost exclusively made up of opposition figures from eight countries.

The Tories will be joined by 29 MEPs from seven other EU countries. Poland's Law and Justice party will be the second largest in the group, with 15 MEPs, while the Civic Democratic party (ODS) from the Czech Republic will provide nine MEPs. The five other countries represented in the group will provide one MEP apiece, making it potentially unstable.

William Hague, the shadow foreign secretary, hailed the founding of the new group, declaring that it dispelled the doubts of critics who said the Tories would struggle to meet the parliament's rules for establishing groups. These groups must have a minimum of 25 MEPs, from at least seven member states.

Hague dismissed “out-of-date and ill-informed” criticisms that Poland's Law and Justice party was homophobic. “The Law and Justice party is a party committed to be against discrimination, for equality under the law,” he told the BBC. Jaroslaw Kaczynski, the Law and Justice leader, underlined his mainstream credentials when he appeared in Warsaw with Cameron on May 29. The former Polish prime minister, whose brother Lech is the Polish president, said “European institutions should be effective, economical, and aid cooperation between member states. They should never interfere with individual rights or the free market.”

But the following day, at a rally in the city of Bialystock, Kaczynski appeared to revert to type. The Economist quoted him as saying “If Europe is to be strong, it has to be Christian. And today it is anti-Christian, and especially anti-Catholic.”

The Tories strongly defend the new grouping on the grounds that it is wrong for the party to campaign on a Eurosceptic ticket in Britain only to sit in the highly federalist EPP-ED group in Strasbourg. Dan Hannan, a Eurosceptic Conservative MEP who wants Britain to leave the EU but to remain in the single market along Norwegian lines, has been pushing this case for the best part of a decade.

Critics of the new grouping cite three objections that it includes a hotchpotch of different parties, some with mainstream views and others with views that would be on the hard right in Britain; that leaving the EPP-ED, which includes Angela Merkel's CDU party from Germany and Nicolas Sarkozy's UMP party from France, will diminish British influence in the European parliament, and that pledging to oppose EU federalism in the European parliament makes no sense because it has little say in deciding institutional changes.

David Miliband, the foreign secretary, said “The Conservatives ... have dragged themselves from Euroscepticism to Euro extremism. By removing the Conservatives from other mainstream centre right parties in Europe, David Cameron has isolated his party and potentially this country.”

— The Guardian, London