Whitehall commissioners have secured the co-operation of Downing Street in implementing a revised civil service recruitment code.

The new code restricts ministers' current right to choose from a pool of candidates, a system that has given rise to accusations of cronyism and politicisation of the civil service.

In future ministers will have to accept the recommendations of a selection panel for appointments from outside Whitehall. They will retain a choice of candidates if they decide to promote internally.

Launching the code, Baroness Prashar, the first civil service commissioner, said: "If the civil service is to be properly equipped, its members must be recruited for their skills and the ability to do the job - that is on merit and merit alone."

If ministers choose to reject the panel's choice, they must gain the explicit approval of the commissioners.

If the commissioners reject the appeal, the competition for the post will have to be re-run.

Repeated refusals from ministers will risk further censure under the new rules.

Welcoming the code, Andrew Turnbull, the cabinet secretary, said: "Recruiting the best people is one of the key ways in which we can ensure that the civil service is equipped to handle the demands of modern-day government".

Sir Andrew said it was important "to maintain the fundamental principle of selection on merit through fair and open means, while ensuring the appointment of civil servants who will be effective in taking forward the work of departments".

"The revised recruitment code brings these roles together in one place. All who are involved in recruitment in the civil service should take the time to explore the new Code," he added.