Firms will be rewarded for encouraging their employees to become part-time soldiers, under plans to shake up Britain's reserve forces and deploy more of them more frequently, according to a long-awaited white paper to be unveiled on Wednesday.

Ministers and defence officials hope direct, though modest, financial incentives for small and medium-sized firms, part of what they call a "corporate covenant", would enable them to achieve their goal – increasing the number of army reservists by more than third, to 30,000 by 2018. By then, the regular army will have fallen to 82,000 from more than 100,000 three years ago.

Companies, for their part, would give undertakings that the career prospects of employees joining the reserves would not prejudice their careers. Large companies would not need financial incentives as they would not suffer the same disadvantages as smaller ones, say defence officials. They could actually benefit from having employees with the experience of having served in the army reserves, officials say.

Companies would benefit from more predictable training programmes, different skills learned by reservists and, more predictable deployments, defence officials say.

The core of the government's £1.8bn plan is to integrate the newly-named Army Reserve more effectively into regular forces so that when they are called up they are better trained and better equipped than the Territorial Army.

A £40m equipment package providing reservists with night sights, upgraded SA80 rifles and GPS satellite systems, will be brought forward. Reservists will be given modern vehicles with mounted weapons systems, and go on more exercises overseas.

Reservists will get better pay better pay and allowances, more on par with the regular army. About a third of the existing TA's 350 training centres will be closed, with reserve battalions based close to large regular army garrisons.

An MoD source said: "With a more professional Army Reserve of 30,000 equipped and trained in a way they have never been before we expect to be deploying them more frequently and therefore increasing the ratio of deployed reservists that is more in line with our international allies."

A senior army officer responsible for the reserves, has warned of possible dangers ahead. "There is the genuine risk that the myriad of change facing the army over the next few years – the end of combat operations in Afghanistan; redundancies of regulars; unit deletions and mergers; withdrawal from Germany; and basing changes – will disenchant and disenfranchise the very people required to deliver it," Brigadier Sam Evans has warned.

"Formalised pairing between a regular and a reserve unit will be the important first step that sets the conditions to deliver integrated capability," he said in a recent paper for the Royal United Services Institute, Rusi.

He added: "It will forge better links to local communities, to employers of reservists and to those leaving the regulars. Establishing the pairing arrangements, along with clarity of roles and locations, provides the conditions for the right people to be recruited into the right posts in the right part of the country."