Pakistan's president alleged that the brother of Pakistan's opposition leader, Nawaz Sharif, "tipped off" the militant group Lashkar-e-Taiba (LeT) about impending UN sanctions following the 2008 Mumbai attacks, allowing the outfit to empty its bank accounts before they could be raided.

Six weeks after LeT gunmen killed more than 170 people in Mumbai, President Asif Ali Zardari told the US of his "frustration" that Sharif's government in Punjab province helped the group evade new UN sanctions.

A month earlier, Shahbaz Sharif, who is chief minister of Punjab, "tipped off" the Jamaat-ud-Dawa (JuD), LeT's charity wing, "resulting in almost empty bank accounts", Zardari claimed in a conversation with the US ambassador to Islamabad, Anne Patterson.

US diplomats were unable to confirm the allegation and noted that they came at a time of rising political tension between Zardari and Sharif. But they conceded that JuD did appear to have received a warning from somewhere. "Information from the ministry of the interior does indicate that bank accounts contained surprisingly small amounts," said the cable in January 2009. A Punjab government spokesman vigorously denied the charge. "There's nothing true in it," said senator Pervaiz Rashid, an adviser to Sharif. "Zardari is our political opponent and he wants to topple our government." Sharif couldn't have known about the UN sanctions, he said, because the UN co-ordinated its action with the federal government and not the provincial one.

The accusation, which has never been publicly aired, is one of several dramas that unfolded behind the scenes after the November 2008 attacks, now revealed by the embassy cables.

US diplomats and CIA spies found themselves playing the role of harried intermediaries to prevent Pakistan and India from going to war. One week after the bloodbath an Indian official said his government was distinguishing between Pakistan's civilian government, "which India believed was not involved in the attacks", and the Inter-Services Intelligence agency (ISI). We are not yet ready to give ISI a clean chit," he said.

Four weeks later the US embassy grew alarmed by Indian plans to release a "sanitised" intelligence dossier that, they feared, could scupper intelligence sharing or thwart efforts to prevent a second attack.

"There are still Lashkar-e-Taiba (LeT) sleeper and other cells in India, Nepal, Bangladesh and Pakistan, as well as many law enforcement leads which need to be pursued," the note said.

Pakistan's generals, usually antagonistic towards India, appeared unusually conciliatory. Six weeks after the attack Pakistan's army chief, General Ashfaq Kayani, said he was "determined to exercise restraint in his actions with India". "If there is any clue about another attack," he told General David Petraeus at his Rawalpindi headquarters, "please share it with us."

His intelligence chief, General Shuja Pasha, went even further, acting as a regional fixer for some of his most bitter enemies. In late 2009 Pasha travelled to Oman and Iran to "follow up on reports he received in Washington about a terrorist attack on India".

He sent warnings to Israel – a country that Pakistan does not officially recognise – "about information about attacks against Israeli targets in India". Earlier in the year, he reminded Patterson, information about a second attack on India had "come his way", which he conveyed to Delhi via the CIA.

The cables suggest Pakistan's ardour for bringing the alleged Mumbai masterminds to justice appears to have wilted as time went on. The secretive trial of Lashkar leader Zakhi ur Rehman Lakhvi and six other suspects "is proceeding, though at a slow pace", US diplomats noted in February.

The secretive trial of Lashkar leader Zakhi ur Rehman Lakhvi, and six other suspects "is proceeding, though at a slow pace" last in February 2010.

ThePakistan's Inter-Service Intelligence agency (ISI) refused access to Abdur Rehman Syed, a retired army major and alleged LeT accomplice. Instead the FBI was told it could "submit questions for Syed through the ISI".

American officials say there is "no smoking gun tying the Mumbai LeT operation to ISI" but are less sure if the spy agency has, as promised, cut all its ties.

"Despite arrests of key LeT/JuD leaders and closure of some of their camps, it is unclear if the ISI has finally abandoned its policy of using these proxy forces as a foreign policy tool," notes a briefing to the US special envoy Richard Holbrooke in February 2009. Dealing with LeT has long been a vexed issue for American diplomats in Pakistan. In March 2006 the US ambassador Ryan Crocker requested the US government to delay by two weeks the designation of JuD.

American helicopters were still delivering aid to earthquake victims in Kashmir, he explained, and they risked attack if still in the area when the designation was approved.

That same month, embassy officials met with Pakistan foreign office director Tasneem Aslam, who told her that Pakistan had "no evidence" linking JuD to terrorism – a conclusion US officials judged "dubious".

Later, in November 2007, the US ambassador presented the foreign secretary, Riaz Khan, with evidence that senior government ministers were publicly helping militant groups, including a declaration from the ministry of defence parliamentary secretary "that he was proud to be a member of LeT and that he seeks to extend support to jihadi organisations when they seek his 'co-operation.'"

"Each of these reports is disturbing in itself, the ambassador said, as they seriously damage Pakistan's image in the international community."

JuD denies that it is a front for LeT.