John McDonnell, the Labour shadow chancellor, is in discussions with the distinguished economist Lord Skidelsky about an independent inquiry into cutting the working week, possibly from the traditional five days to four.

The academic, who has a longstanding interest in the future of work, confirmed he was talking to the shadow chancellor about “the practical possibilities of reducing the working week”.

Skidelsky said he did not want to “be too exact” about his recommendations, although he added the idea of exploring ways of reducing the traditional five-day week to four was under consideration.

McDonnell has suggested the party could ​include a pledge to reduce the traditional working week by a day in its manifesto for the next election. Asked directly about this last month in a BBC interview, ​he said: “We will see how it goes.”

The idea, though, is sensitive in Labour circles with some ​unsure whether such a commitment would be appropriate. The idea was floated during the ​Labour conference in September ​but the party later denied it was being considered – before McDonnell reignited speculation about it in the BBC interview.

Labour insiders say that people work too many long hours but some argue that issues such as zero-hour contracts and other issues faced by gig-economy workers are more pressing.

Skidelsky indicated he did not anticipate holding an official party inquiry, saying that he hoped to produce work that would be “open to anyone to look at the results”. Workers in France and Germany produce more than their British counterparts, despite working shorter weeks.

Further clarity on the topic is expected in around a fortnight. When McDonnell was asked on Tuesday directly about Skidelsky advising him on a four-day week, he said: “I’ll get back to you on that. I’ll let you know in the next couple of weeks”.

The shadow chancellor added that he was reading a new book by Skidelsky, entitled Money and Government, describing it as “terrific”.

Frances O’Grady, the TUC general secretary, said that a four-day week should be “an ambition” at ​its annual gathering in September. At the time Brandon Lewis, the Conservative party chairman, responded by saying the idea would do “untold damage to our economy”.

Skidelsky, who sits as a crossbencher in the Lords, is an emeritus professor at Warwick University and has previously written a three-volume biography of Lord Keynes as well as on the financial crisis.