A legal challenge has been launched over the government’s apparent attempt to force the charities’ watchdog to pursue a regulatory agenda against good causes that ministers believe stray into “woke” and “political” activities.

The Good Law Project has served a pre-action letter claiming ministers’ stated intention is to make it a condition of appointment that the new chair of the Charity Commission in effect pursues “the current political agenda of the Tory party”.

It says an instruction issued by the former culture secretary Oliver Dowden last week before interviews for the post is unlawful and “amounts to an impermissible and improper attempt on the secretary of state’s part to direct and control the exercise of the new chair’s regulatory functions”.

The move follows increasing concern in the voluntary sector that charities are being used as “fodder for phoney culture wars” as hostile Tory MPs and ministers criticise a range of legitimate charitable activities, from brand name changes to blogposts and the discussion of race and the UK’s colonial history.

Dowden published an opinion article in the Daily Telegraph and on the Department for Digital, Culture, Media & Sport (DCMS) website last weekend to attack what he called “a worrying trend in some charities that appear to have been hijacked by a vocal minority seeking to burnish their woke credentials”.

He cited the example of the Churchill Fellowship, which was criticised by the prime minister Boris Johnson over media reports it had changed its name in an attempt to “airbrush” out Sir Winston’s name. This was described as untrue by the fellowship, as well as the Churchill family, which said it wholly supported the name change.

Dowden said he had instructed officials to ensure candidates for the Charity Commission chair role were “tested” on how they would use the watchdog’s powers to rebalance charities by “refocusing” them on their founding missions. “Ministers will only select a candidate that can convince on these criteria,” he added.

Under charity law the secretary of state can appoint the regulator but is expressly prohibited from directing or controlling the actions of the appointee. The Good Law Project has called for the interview process to be paused, and to be re-run lawfully.

The Good Law Project letter says: “It is clear … the rebalancing exercise referred to is the use of the commission’s powers to prevent or deter charities from decisions and activities which the secretary of state refers to as “woke” – that is, which arise from a focus on and awareness of the existence and consequences of racial prejudice and discrimination.”

Jo Maugham, director of the Good Law Project, said: “We don’t think it’s the Charity Commission’s job to muzzle or “cancel” charities that don’t push the government’s agenda. And we certainly don’t think it’s lawful.”

Dowden’s comments were widely criticised in the voluntary sector. Sarah Vibert, the interim chief executive of the National Council for Voluntary Organisations, said: “Expecting the Charity Commission to go beyond its role – a role that is defined in law – will harm the new chair’s independence and is setting them up to fail.”

There have been three unsuccessful attempts by Conservative MPs to force the regulator to act against well-known UK charities in the past few months. The National Trust, Barnardo’s and the Runnymede Trust have been accused of breaching charity law by pursuing a “woke” ideological and political agenda.

In each instance the Charity Commission carried out a regulatory compliance check and subsequently exonerated each of the three charities, reaffirming that within the law, charities “are allowed to campaign and to take controversial positions in support of their purpose”.

The commission is the independent regulator for charities in England and Wales, overseeing 168,000 charities and more than £80bn of charitable income.

Dowden was succeeded as culture secretary by Nadine Dorries in this week’s reshuffle, moving to co-chair of the Tory party, but his opinion piece remains on the DCMS site.

A DCMS spokesperson said the chair of the Charity Commission would be appointed “following fair and open competition”.

It said it had received correspondence from the Good Law Project and would respond in due course.