The foreign secretary has said there can be "no excuses" for failing to reform the Palestinian Authority.

Speaking as the government began a key conference aimed at breathing new life into the stalled Middle East peace process, Jack Straw called on Yasser Arafat to back more democratic governing arrangements.

The talks will involve delegates from the United States, United Nations, the European Union, Russia, Jordan and Egypt.

But Palestinian representatives will be limited to participating via videophone, having been banned from travelling to London by Israeli premier Ariel Sharon.

"The important thing about these discussions is that they are there to try and accelerate the momentum towards internal reform in the occupied territories, the West Bank and Gaza, for the Palestinian Authority," Straw told BBC Radio.

"Now, having this conference by video link is obviously less satisfactory than a face-to-face conference and it is no substitute for a face-to-face conference, but it will still, I believe, be very useful."

And the foreign secretary rejected suggestions that Israel's current security clampdown in the occupied territories made the reform process impossible.

"One of the points that I will be saying to the Palestinian Authority representatives today is of course we understand that the fact of occupation, of the siege, the fact that leaders of the Palestinian Authority can't even travel between different parts of the West Bank, still less come to London, is a major impediment in terms of day-to-day administration.

"But that cannot be used as an excuse to stop the reform process in its tracks, and I think, in fairness to them, they will say yes they agree and we will then discuss the progress that is needed."

Reform issues expected to be discussed included the creation of a prime minister's office, as well as a Cabinet and legislative council with an independent judiciary.

An overhaul of the Palestinian Authority's finances is also being considered.