A veteran Democratic foreign policy adviser has accused Bill and Hillary Clinton of nepotism, dishonesty and vindictiveness in an assault on a previously untouched part of the Clinton political legacy – Ireland.

Trina Vargo, who was a behind-the-scenes Washington player in Northern Ireland’s peace process, claims the couple tried to obtain a scholarship to Ireland for a boyfriend of their daughter, Chelsea, and later cut funding for the scholarship to punish Vargo for backing Barack Obama in the 2008 Democratic presidential nomination race.

Vargo makes the allegations in a book, Shenanigans: the US-Ireland Relationship in Uncertain Times, published this week in the run-up to St Patrick’s Day celebrations.

It lifts the lid on what Vargo sees as inept, deluded and, at times, farcical efforts by Irish politicians and officials to tap the Irish diaspora and potential allies in Washington and Hollywood.

Vargo, who founded the US-Ireland Alliance, a Washington-based non-profit organisation, shuttled between the US capital, Dublin and Belfast for two decades while advising Sen Ted Kennedy and the Clinton and Obama administrations on Northern Ireland.

Her portrait of the Clintons casts a shadow on a jewel of their foreign policy legacy, alleging pettiness and vengefulness after the historic peace-making of the 1998 Good Friday agreement.

Angel Urena and Nick Merrill, spokespersons for the Clintons, defended the couple and rejected the book’s claims. “Their legacy there is something they are incredibly proud of and one that is well documented. These accusations are baseless and patently false.”

Vargo set up a scholarship named after George Mitchell, a former US senator who helped broker the agreement, in 1999. It sends 12 US students to study in Ireland and Northern Ireland each year.

Vargo writes that in November 2000 Mitchell told her “with some uneasiness” that Bill Clinton, then nearing the end of his time in the White House, had phoned him to say he was “very unhappy” that Chelsea’s boyfriend had not been shortlisted from about 200 candidates despite a recommendation letter from the president.

Mitchell made clear he was not asking for the boyfriend’s inclusion, just seeking clarification. “It would be hard to believe that the timing of the president’s call wasn’t aimed at influencing us to make him a finalist,” writes Vargo.

The boyfriend remained off the shortlist, which Vargo believes put her on a path to joining the Clintons’ “enemies list”.

In 2007, Vargo advised Obama’s campaign on Ireland policy during his battle against Hillary Clinton for the Democratic nomination. Clinton challenged her rival’s lack of experience and promoted her role in the peace process as first lady.

Clinton and her supporters grossly exaggerated her influence, says Vargo. “The tall tales just kept growing … disregard for the truth was not invented, merely taken to new heights, by Donald Trump in the 2016 campaign.”

Vargo helped Obama’s campaign to challenge the former first lady’s version, leading, she believes, to “payback” months later when Bill Clinton cancelled his attendance at a US-Ireland Alliance event in Belfast to celebrate the Good Friday agreement’s 10th anniversary.

There is no proof to back up the claim. An aide told Vargo a scheduling change was behind the decision and declined to elaborate.

In 2012, the state department, then under Hillary Clinton, cut its annual $500,000 contribution to the Mitchell scholarship, citing budgetary measures. “The elimination of funding … was not about the money,” Vargo writes.

The Clintons’ spokespersons said Clinton’s successor, John Kerry, also cut funding. “Both [were] the product of a constant battle with a Republican Congress to fight for diplomatic and development dollars, there is nothing more to it than that.”

Since 2015, Vargo has filed freedom of information requests to clarify the reason for the funding cut, supplying a list of names to the state department, but has only received documents with other, lower-level names.

The book also levels accusations at Irish politicians and officials. Successive Irish governments brought a “begging bowl” mentality to Washington by seeking funding for peace process initiatives long past their sell-by date, she says.

They also made clumsy efforts to tap the diaspora, such as creating the “certificate of Irishness”, a scheme scrapped for lack of interest in 2015, and annoyed Latinos and other groups in the US by unsuccessfully seeking special deals for Irish immigrants.