The coalition government will be accused of maintaining pointless ministerial jobs to maintain influence over crucial parliamentary votes, in a report released on Monday.

The public administration select committee, that scrutinises Whitehall, claims David Cameron's government is "patronage-driven" and is spending public money to buy loyalty. The damning verdict follows government rejection of committee proposals to cut ministers and parliamentary private secretaries in line with a proposed reduction of MPs. It follows criticisms that the coalition is failing to cut senior jobs in its drive to slash costs across Whitehall.

Bernard Jenkin, the Conservative chair of the committee, said the government's promise to keep ministerial numbers "under review" was political code for "their refusal to engage with the committee on this recommendation. There are more than a dozen unpaid ministers in this government – a practice described to us by one eminent witness, Peter Ridell, as "an abuse".

"The number of ministers in the Commons is at its absolute limit. There are more PPSs than we consider necessary. This is more about exercising patronage over MPs, and thus being able to influence debates and votes, than it is about efficiency and accountability," he said.

In March, the committee released a report titled Smaller government: what do ministers do?. It called for cuts in ministers to match proposed government cuts in MPs from 650 to 600.

There are 121 MPs on the "payroll vote'' as ministers or their parliamentary aides who are obliged to vote with the government or resign.

The committee said the payroll should be slashed by more than 60 within four years. Many ministers were engaged in tasks better carried out by officials, and parliamentary aides performed "few functions of real value", said the March report. The payroll vote makes up a "deeply corrosive" 22% of the Commons.

But that would rise to 23.5% unless at least eight ministerial posts were cut, it found.

Under the recommendations put forward by the committee, junior ministers would no longer enjoy a Commons aide – cutting PPSs by 26.

It also called for an end to the appointment of unpaid ministers to circumvent legal limits on the size of government and a review of numbers by the mid-point of the present parliament.

Monday's report discloses that the government has promised to keep numbers under review but says the proposed cuts are unlikely, angering the committee.

"If the government feel they need so many ministers to control the apparatus of government, that is because there is no strategic plan for civil service reform, which would make the Whitehall command chain much more responsive to ministers. "No number of ministers is a substitute for effective leadership in Whitehall departments," said Jenkin, MP for Harwich and North Essex.

Government sources said it had "acted decisively" to reduce costs by cutting 5% off ministers' pay and agreeing to reform their pensions. The number of ministers and aides will be "kept under review".