Downing Street is being accused by Labour of flouting Whitehall rules to hire a new White House-style spokesperson to host daily government press conferences on live TV.

A new special adviser is being recruited to reply to questions from journalists including rebuffing criticisms from opposition politicians.

But the special advisers’ code of conduct stipulates that politically appointed staff cannot speak publicly or engage in political controversy.

The Cabinet Office is aware that the rules will be interpreted at the discretion of Boris Johnson.

Labour has criticised the move, amid concern that Dominic Cummings is dropping the previous practice of asking ministers to answer for government policy.

The shadow Cabinet Office minister, Rachel Reeves, told the Guardian: “Once again, this government is showing its willingness to play fast and loose with the rules when it comes to Boris Johnson’s closest advisers. And once again, they are showing contempt for the most basic requirements for accountability.

“Elected politicians answerable to parliament should be delivering the government’s messages; not well-paid appointees accountable to no one but the prime minister.”

The job advert placed on the Conservative party’s website has led to speculation that the government is hoping to employ a broadcaster who may already be well known to the public.

Placed on the Conservative LinkedIn page, the advert describes the job as a chance to “communicate with the nation on behalf of the prime minister”.

“Essential skills” include “excellent risk management and crisis communication skills”.

US presidential spokesmen such as Sean Spicer and Anthony Scaramucci became household names, and found themselves at the centre of controversy.

But in the UK, twice daily media briefings have been held behind closed doors, with a civil servant taking questions from a group of accredited journalists, known as the lobby. Questions regarding party matters are referred to the political party’s spokespeople.

Under the new plan, a special adviser – a politically appointed civil servant who answers directly to a minister – will answer questions in front of television cameras.

According to point 14 in the special advisers’ code of conduct, “special advisers must not take public part in political controversy, through any form of statement whether in speeches or letters to the press, or in books, social media, articles or leaflets … briefing on purely party political matters must be handled by the party machine.”

A senior government source suggested it was a normal “special adviser” job and the code was at the discretion of the prime minister. As EU negotiator, David Frost is among those classed as special advisers but who have also given high-profile speeches, notably in February when he set out the UK’s vision for Brexit.

In a further development, the union for senior civil servants has claimed that the Cabinet Office has confirmed suspicions that cabinet ministers are no longer expected to choose their special advisers.

A senior official from the propriety and ethics team wrote to the FDA union on 14 July to say that an appointing minister as well as the prime minister are expected to agree before a “spad” is taken on.

“I can confirm that it is still a requirement for the appointing minister, as well as the prime minister, to agree to the appointment of a special adviser,” the official wrote.

The ministerial code says it is cabinet ministers who choose their advisers, who must then be approved by the prime minister.

Dave Penman, the head of the FDA, said the letter showed a power shift that had left special advisers with few employment rights.

“It is now clear that ministers are expected to approve their allocated special adviser from No 10, a complete reversal of the arrangements envisaged under the ministerial code.

“As we witnessed with the resignation of former chancellor Sajid Javid, even the most powerful ministers in cabinet are expected to accept the advisers picked for them by No 10.

“Special advisers are now left without security of employment, can be dismissed almost at will by the PM and are under the direct management of Dominic Cummings. These changes are not about effective government, but more effective control for No 10,” he said.

A Whitehall source insisted that there had been no fundamental change.