The Brexit impasse paralysing the government over the last 19 months could undermine the British armed forces, a thinktank has warned.

The Royal United Services Institute (RUSI) said on Tuesday (6 February) that uncertainty about Brexit had engulfed the armed forces sector and caused severe delays in vital decisions on axing warships, aircraft and regiments.

"The government is increasingly perceived to be unable to make difficult decisions, distracted by Brexit and unable to play an international role that is commensurate with the resources it devotes to this purpose," Prof Malcolm Chalmers, the thinktank deputy director and adviser to parliament's joint committee on national security strategy, said.

"The longer this policy paralysis continues, the greater the risk to the UK's reputation as a reliable ally, and the stronger the (unfair) perception that it is no longer capable of being a serious security player.

"With talks on the EU's future relationship with the UK approaching a critical moment, this is not a helpful message."

The Ministry of Defence was due to publish a review earlier this year, which would have seen planned military reductions implemented. However, the publication of the report has been postponed until the summer, a move that jeopardised Britain's reputation as an international partner, warned the thinktank.

RUSI warned that by extending the review process, the MoD was running the risk of damaging Britain's "credibility as a serious security actor" while the ministry faces a budget shortfall of approximately £20bn over the next decade.

British troops training
The thinktank said MoD would have to embrace technological change Getty Images

Chalmers added that he expected to see cuts to traditional forces, such as a reduction in the overall size of the full-time army. At present that stands at 77,440, although it is supposed to count on 82,000 units. Gaps could be filled by greater use of reservists, he added.

"The review is likely to involve some sacrifice of lower-priority capabilities, including those that have enjoyed a degree of political salience in public debate," he said.

The thinktank also highlighted that the MoD would have to swiftly adapt to a major technological change to be better equipped to counter potential cyber and electronic warfare threats.

"The more radical the commitment to rapid fielding of new disruptive technologies, the less useful the traditional measures of military capability – numbers of ships, manned combat aircraft and regular full-time army personnel – become as indicators of national military power," Chalmers said.