The Palestinian leadership has stepped up its attack on Tony Blair in his role as envoy of the Middle East Quartet, saying that his "parroting" of Israeli demands casts doubt on his credibility.

Nabil Shaath, a senior Palestinian official, confirmed that Palestinian leaders had discussed whether to make a formal request to the Quartet that Blair be removed from his position, but had decided against such a move.

"Everyone had reservations about Blair's performance, but we don't want to embarrass him any more," Shaath said. "If you want to do it, you wait until things have quietened down."

Hostility towards Blair, who has been the Quartet's envoy since soon after leaving Downing Street in 2007, has hardened in recent weeks.

Blair acted as a "defence attorney" for the Israelis during a debate within the Quartet in July, when its partners – the US, EU, Russia and the UN – were unable to agree on a statement on the outlines of a return to peace talks. This, Shaath said, gave cause for "serious doubt that he could carry on his duties" as a neutral. He described Blair as "a personal friend, a brilliant man, extremely intelligent, with an important record of achievement, at least in his early years".

When he took on the role of Quartet envoy, "we thought he would be a real support to the Palestinians. But he gradually reduced his role to that of asking the Israelis to take down a barrier here or a barrier there… He really escaped all the political requirements of his job as representative of the Quartet."

In fact, Blair's remit from the Quartet was restricted to easing economic constraints in the West Bank and Gaza and helping with state-building. He was asked to take on the role of political mediator by the US only in the run-up to the Palestinians' demand for full membership at the UN. "He was parroting exactly what the Israelis wanted," said Shaath.

However the Quartet's eventual statement "had few flaws, if any". Its call for restraint on provocative actions was clearly intended to encourage the Israelis to curb settlement expansion, he said. But Israel's announcement last week of 1,100 new homes in the settlement of Gilo was a rejection of the statement and an indication of its intent to continue its "land grab", according to Shaath.