Tate Britain has defended an advert for a head of coffee with a salary of nearly £40,000 – more than the average wage of a London-based curator – after critics said the role highlights how low museum professionals’ wages are.

The wage comparison site Glassdoor states that the average annual wage for a curator based in London is £37,300. The Prospect union said the pay discrepancy was a reminder of how badly paid museum professionals are in comparison with other jobs in the arts sector.

Alan Leighton, Prospect’s national secretary, told the Guardian that heritage-specific roles were paid “appallingly”, despite the fact that without qualified specialist workers there would be no galleries or museums. “It’s time that was recognised and those roles rewarded accordingly,” he said.

“The pay discrepancy highlighted is a stark reminder, not that the head of coffee is paid too much but that highly qualified museum professionals are paid far too little.”

The gallery defended the £39,500 head of coffee position, which Tate began advertising for last week, saying it was unfair to compare a head of department with a curatorial role of a different level.

“All Tate’s departments have a variety of roles with different responsibilities and salaries, including curatorial, and a more accurate comparison would be a curatorial team leader,” Tate’s statement read. “We value all our staff and strive to pay them appropriately for their work at Tate.”

Tate confirmed that a curatorial team leader wage would range from £40,000 up to £50,000, depending on the size of the team.

In 2017, the Museums Association said that low pay was widely recognised as a major problem for the sector and that wages were falling behind that of comparable sectors and were “barely keeping up with the cost of living”.

In the same year, the Museums Association published guidelines and research, which identified that wages for assistant curators were 25% behind pay rates for similar roles in other sectors. It found that curator pay spanned from £17,524 at its minimum acceptable annual rate to £50,078 for a minimum wage as a senior head of collections.

The artist Grayson Perry tweeted a story about the role, with the comment: “I give up, they’ve won.” The artist did not respond to the Guardian’s request for comment but others called the role “depressing” and “disgusting”.

The advert tells candidates the role “encompasses all aspects of coffee” within the four Tate galleries and requires them to have “extensive experience of cupping and espresso quality assessment”, while experience of developing blends for espresso and filter coffee is a must.

The position is part of Tate Eats, the commercial business and trading arm of Tate Enterprises Ltd – a wholly owned Tate subsidiary – which is responsible for events including “William Blake & lunch” where visitors can get access to the Blake exhibition and have a three-course meal at the Rex Whistler restaurant for up to £45, plus service charge.

Tate Britain houses the Roastery at Tate, described on its website as “a diverse and innovative specialty coffee space” that is home to the company’s Gender Equality Coffee Project and Slot Roasting Collective, “a vibrant community-led non-profit business that helps fund Tate Gallery and champion coffee producers and professionals of all genders throughout the coffee value chain”.

The head of coffee role requires blending and roasting coffee for use in all Tate Eats’ sites and managing the hot beverage team, while being responsible for “all aspects of tea and coffee”, and managing a slot-roasting programme, plus wholesale and white label contracts.

Research from the British Coffee Association found that the UK coffee industry’s total contribution to the UK economy was £17.7bn in 2017, and that the sector creates about 210,325 British jobs.

• This article was amended on 31 January 2020 because an earlier version suggested the role of “head of coffee” was advertised by Tate Britain. Tate advertised the role, which has will be based at Tate Britain.