Some 70,000 retail jobs were lost in the final months of 2018 and nearly a third of retail businesses plan to shed staff in the coming months, according to a new report that underlines the tough trading conditions on the high street.

The survey, carried out by the British Retail Consortium, came as John Lewis revealed it is to close its smallest department store, Knight & Lee in Southsea in Hampshire, putting 127 jobs at risk.

The retailer’s parent group also said it is to outsource 365 maintenance jobs at its department stores, Waitrose supermarkets, its distribution network and head office. The shake-up means that after next year, the workers affected will lose the annual profit-related bonus paid to all staff directly employed by the employee-owned group.

Retailers are under intense pressure as shoppers rein back spending, switch their purchases online and prioritise spending on leisure and holidays. At the same time many retailers’ costs have been rising, as a result of higher minimum wage levels and increased business rates.

The BRC survey also showed that hours for both full time and part-time shop staff had been reduced. Helen Dickinson, chief executive of the BRC, said: “The retail industry is undergoing a profound change and the latest employment data underpins those trends.”

Earlier this month John Lewis said it was considering suspending its staff bonus for the first time in 66 years as it warned that profits would be substantially lower this year after the worst Christmas for retailers since the depths of the financial crisis.

The 35,000 sq ft Knight & Lee store, which has been open since at least 1887 and was bought by John Lewis in 1934, is due to close in July.

John Lewis said it had decided to close the store, which is the only outlet to officially retain its original name apart from Peter Jones in London, as the site needed “significant investment to modernise” and it had received a good offer for the freehold.

It is understood the site has been bought by a property firm, That Group, which plans to redevelop it.

Sign up to the daily Business Today email or follow Guardian Business on Twitter at @BusinessDesk

John Lewis said it was not planning other closures.

Dino Rocos, the operations director at the John Lewis Partnership, said the company was attempting to find suitable roles for as many staff as possible but there would be redundancies.

“We have not taken this decision lightly and we considered every implication for our [staff], customers and the community. However, a unique combination of factors, including the significant investment required and the opportunity to sell the property freehold, makes this the right decision for the financial sustainability of our business,” he said.