A senior Kurdish intelligence official has claimed that both Britain and the US were alerted to the possibility of the Islamic State of Iraq and the Levant (Isis) leading a Sunni awakening through Northern Iraq but warnings "fell on deaf ears".

Rooz Bahjat, a senior lieutenant to the head of Kurdish intelligence Lahur Talabani, told The Daily Telegraph that both the British and US governments ignored new information that Isis were to strike a deal with leading Sunni figure Izzat al-Douri, the former Baathist deputy of Saddam Hussein and current leader of the Islamic Army of Iraq.

The agreement between the two Sunni factions would lead to the takeover of Iraq's second city, Mosul, and the capture of other Iraqi cities and towns as the coalition storms south towards Baghdad.

Bahjat claims that a Kurdish intelligence "asset" had information of the deal five months ago after the fall of the two Sunni cities of Fallujah and Ramadi to Isis.

"We had this information then, and we passed it on to your (British) government and the US government," Bahjat said. "We used our official liaisons.

"We knew exactly what strategy they were going to use, we knew the military planners. It fell on deaf ears."

The Islamic Army of Iraq is fighting alongside Isis against the "common enemy" of Iraq's Shia prime minister Nouri al-Maliki.

"Is it possible that a few hundred Isis jihadists can take the whole of Mosul?," asked the group's co-found Sheikh Ahmed al-Dabash.

"No. All the Sunni tribes have come out against Maliki. And there are parts of the military, Baathists from the time of Saddam Hussein, clerics, everyone came out for the oppression that we have been suffering."

Different Sunni groups have come together despite their differences to tackle al-Maliki's regime after accusations of torture, murder and harrassment on the part of his armed forces against Sunni Arabs.

The Foreign Office said it refused to comment on matters of intelligence.