BERLIN, June 30 (Dave Graham/Reuters) - The international community must pursue negotiations with Hamas if it wants to reach a two-state solution for Israel and the Palestinians, Germany's main opposition Social Democrats (SPD) said on Wednesday.

Following the Nazi genocide of European Jews in World War Two, Germany's main political parties have been staunch supporters of Israel and strongly critical of Hamas, which refuses to recognize Israel.

However, dismay over the Israeli 2008 invasion and blockade of the Hamas-controlled Gaza Strip has led to increasing German readiness to question policy in Israel, which considers Hamas to be a terrorist organization and refuses to negotiate with it.

Rolf Muetzenich, foreign policy spokesman of the center-left SPD, told Reuters the success of Islamist parties in the Middle East meant ignoring them was no longer an option if politicians were serious about creating lasting peace.

There's no official decision (to recognize Hamas), but we have to understand they are a movement that is now part of the political landscape in the region, he said. We must at least recognize that we need to have dialogue.

Following Israel's storming of a Gaza-bound aid convoy last month, foreign policy experts from Chancellor Angela Merkel's centre-right coalition and their opposition counterparts on the center-left took the rare step of agreeing a joint initiative to demand an international investigation into the incident.

Muetzenich, a Middle East expert, likened the situation with Hamas to Britain holding secret talks with the Irish Republican Army during the years of conflict in Northern Ireland.

There are parallels here between the IRA and the British government during the Northern Irish conflict, he added. The British government carried on negotiations with the IRA behind the scenes even though it described the IRA as terrorists.

Muetzenich said it was vital that policymakers redoubled efforts to prevent splits from widening between Hamas and the Fatah faction of Palestinian President Mahmoud Abbas.

Given that a number of political organizations in the region with Islamist roots now held positions of power, western nations like Germany -- now home to over four million Muslims -- had to start coming to terms with local sentiment, he said.

We can't talk to (Turkey's ruling) AK Party and forget they came from an Islamist movement, he said. We also need to grasp the fact that Hezbollah is a part of the government in Lebanon. (Editing by Myra MacDonald)