The number of federal government ministerial advisers has ballooned 65 per cent since last year, prompting union claims that the Coalition is trying to get around its own 2 per cent cap on public-­sector wage rises.

Department of Finance documents show the number of staff classified as senior advisers jumped from 61 in February last year to 101 last month.

In the same ­period, the number of staff in lower-paid positions fell by eight.

Hundreds of parliamentary staffers, who have not had a pay rise for two years, have started voting on a new enterprise agreement that limits annual wage increases to 2 per cent.

The United Services Union ­accused the government of promoting dozens of advisers in a bid to subvert the public-sector pay cap. It said advisers stood to gain wage rises of up to $50,000.

Union secretary Graeme Kelly said the government appeared ­engaged in a “cynical attempt to game the system, providing substantial pay rises to staff members in ministerial offices at the same time that other employees had been left without any pay rise since 2014”.

“What these documents reveal is that while staff members in electorate offices across the country have gone without a pay rise for two years, the government has ­secretly been providing huge ­financial bonuses to dozens of ­employees in the offices of ministers,” Mr Kelly said.

“In public, they preach the need for frugal pay rises for public servants that barely keep pace with the cost of living, but in private they are rewarding their own advisers with pay rises of up to $50,000 a year.”

Senator Scott Ryan, speaking as Minister Assisting the Cabinet Secretary, said attempts by the union to link staff levels to the proposed enterprise agreement were “disingenuous”.

“All government staffing appointments are made on merit in line with an applicant’s experience qualifications,” Senator Ryan said.

He said in recent months, political parties had received increases in personal staff numbers.

“The proposed enterprise agreement, negotiated by the bargaining representatives and approved by the Australian Public Service Commissioner includes a fair and affordable pay rise of 2 per cent for all staff and no loss of conditions,’’ Senator Ryan said.

Mr Kelly said many senior ministerial staff had encouraged colleagues to vote in support of the federal government’s wage offer “without revealing that they had benefited from substantial pay ­increases during the past year”.

“With no pay rise since 2014, the pay rates of most staff won’t even keep pace with inflation,” he said. “Meanwhile, at least 40 staff in the offices of government ministers have been granted huge pay rises.

“The federal government’s double standards are shown clearly by their gaming of the parliamentary wage system, where the chosen few receive huge financial rewards, while hundreds of other hard-working public servants are left in the cold.”

Josh Manuatu, an adviser to former employment minister Eric Abetz and Coalition staff bargaining representative, said he had ­received positive feedback about the pay offer from government workers.

He said Coalition staffers were keen to get a pay rise by Christmas and accepted that the wage offer should be in line with the increase offered across the public sector.

The Australian