The first world war centenary commemorations risk being overshadowed by moves by the Imperial War Museum to privatise its visitor services, a trade union has warned.

Bids for the £10m contract have been submitted and and it is understood that a decision will be made next week on the future of the visitor services.

The museum is transforming itself in the wake of major cuts in its government funding which have left it looking for increased private-sector funding. Around 200 staff are currently employed in visitor services.

Expressing concern about the privatisation, the Public and Commercial Services (PCS) union warned of its potential effect as the IWM prepares to play a central role in First World War Centenary commemorations.

According to PCS, a new company would take over on 1 April 2014, just two months before the museum in Lambeth, south London – the IWM's flagship branch – is due to open what it describes as "groundbreaking" new galleries for the centenary.

The museum is also planning a "new major exhibition" in Manchester and boasts of leading a global network of more than 1,600 cultural and educational organisations for the commemorations, due to run until 2018.

PCS says it fears that handing visitor services and security to a profit-making company will lead to cuts in jobs and standards, and a knowledge drain from the institution, which also runs HMS Belfast, the Churchill War Rooms, the Duxford air museum in Cambridgeshire and IWM North in Manchester.

The union has accused museum management of refusing to provide information on costing or how service standards would be monitored, and says the companies believed to be in the running have little experience of providing the full range of visitor services currently provided by in-house staff.

With tenders invited against a backdrop of a cut in the museum's budget from the Department for Culture, Media and Sport, the proposal is being driven by a desire to reduce costs, not improve services, PCS said.

Its general secretary, Mark Serwotka, said: "Next year government ministers will take every opportunity to use the first world war commemorations to their advantage, while at the same time putting at risk the first-rate services and expert advice on offer at the musuems.

"Not only would gifting this work to a profit-making company put jobs on the line, it would be a major gamble with the reputation of some of our best-loved visitor attractions at a time when the eyes of the world will be on them."

A spokesperson for the museum said: "There will be a number of meetings over the coming weeks to discuss the recommendations as a result of the comprehensive visitor services review, to reach a decision about next steps and communicate these to the teams across IWM. This review has taken into consideration cost and quality of service, both being of equal importance to IWM. The outcome of this review will not impact the first world war centenary commemorations."