The government has appointed Althea Efunshile, a former deputy chief executive of Arts Council England (ACE), to the board of Channel 4, in a dramatic U-turn after the culture secretary blocked her appointment a year ago in favour of four white men.

Efunshile was the only one of five candidates for Channel 4’s board rejected by Karen Bradley in November 2016.

Ofcom is responsible for finding, vetting and appointing Channel 4 non-executive directors, with the Department for Digital, Culture, Media and Sport usually rubber-stamping its decisions.

Bradley’s unusual move to step in to reject Efunshile, which at the time meant three of Channel 4’s 13 board members were women and all were white, embarrassed the government.

Bradley’s unusual move to step in to reject Efunshile, which at the time meant three of Channel 4’s 13 board members were women and all were white, embarrassed the government.

The announcement came on the same day as a green paper on corporate governance was published that highlighted the importance of “improving the diversity of boardrooms so that their composition better reflects the demographics of employees”.

Theresa May was forced to defend Bradley’s decision after the Labour MP David Lammy used prime minister’s questions to ask whether she thought there “isn’t a woman or a black person in the country worthy of being on the board of Channel 4?”

The DCMS said at the time that it approved only the candidates who “met the specific skills and experiences set out in Ofcom’s advertised job descriptions”.

However, the regulator said all five candidates it put forward were of a “high calibre”.

Efunshile, who was appointed deputy CEO of ACE in 2012, received a CBE in June 2016 in the Queen’s birthday honours for services to arts and culture.

She was also made the first chair of the National College for the Creative and Cultural Industries.

A dozen of the most respected female figures in the arts and creative industries, including the playwright Bonnie Greer, the former culture secretary Tessa Jowell, the former cabinet minister Valerie Amos and Gail Rebuck, the chair of Penguin Random House UK, called on the government to explain its decision.

On Tuesday, the DCMS announced Efunshile as one of four new non-executive directors on the Channel 4 board. Industry sources told the Guardian after the rejection last year that Efunshile would be included in the next wave of appointments.

Tom Watson, the deputy Labour leader, called on the government to explain why it had “wasted a year” appointing Efunshile.

“Althea Efunshile is a very good appointment to the Channel 4 board, but she would have been a very good appointment a year ago, too, when ministers blocked her,” he said.

“After she was blocked, Matthew Hancock [digital minister] attacked ‘tokenism’ and said that board members had to be appointed on merit. The government should explain what has changed, and why they wasted a year making this decision.”

A DCMS spokesman defended Bradley’s decision-making, saying Efunshile met the criteria for a different non-executive role at Channel 4, one that required a person with “experience working and/or engaging with young people, for example from an organisation with an educational purpose”.

An Ofcom spokesman said: “The secretary of state approves candidates on the basis that they meet the specific skills and experiences set out in Ofcom’s advertised job descriptions.

“Althea’s experience in the educational and cultural sectors will help make sure the interests of young people are represented at board level, and she was the best candidate for this particular role.”

The DCMS also approved Ofcom’s selection of Tom Hooper, the director of the King’s Speech, Fru Hazlitt, a former senior executive at companies including ITV, Yahoo and Virgin Radio, and Uzma Hasan, a producer and co-founder of Little House Productions.

The number of members on Channel 4’s board is flexible, with the four new appointments replacing three departures in Josie Rourke, MT Rainey, and Paul Potts.

The Channel 4 chairman, Charles Gurassa, said: “I am delighted to welcome Althea, Fru, Tom and Uzma to the Channel 4 board.

“They bring an impressive track record of creative and commercial leadership in both the public and private sector. I know that they all share great admiration and enthusiasm for the work of Channel 4 and the importance and value of its public service remit.”