Big business must be stopped from accessing “unlimited pools” of foreign labour that keep British wages low, Boris Johnson will say in a speech urging cabinet ministers to “focus on the issues that drove Brexit”.

For too long, major corporations have held wages down by bringing in workers from overseas, the foreign foreign secretary is expected to tell workers at the JCB headquarters in Rochester on Friday.

“But there must be a balance,” Johnson is set to say, calling himself a “passionate believer in the benefits of migration”.

“And if an influx of labour is being used not only to prevent investment in capital equipment but also in the skills and prospects of young people, then we need to think carefully about how we control immigration.”

Johnson – who has long been considered a contender for Tory leader – is set to give his keynote speech just days after Parliament handed Theresa May and her Brexit deal a cutting blow, with the government suffering a historic defeat.

But, setting out his vision of post-Brexit Britain, he will say that ministers must do more than just control immigration if they want to give people a pay increase, calling on the government to address the “worrying” productivity gap between London and other parts of the UK.

“If you look at the distribution of the Brexit vote, it is clear that people felt that gap in attainments and prospects and that they wanted something done,” the staunch Brexiteer will say.

“If we are to bring our nation together that means investing in great public services and safer streets, better hospitals, better transport links and better housing.”

The former London Mayor will also use the moment to call for “the most favourable tax environment”, saying no-one should pay more than 50% of their income in tax.

“Not because we want to create a tax haven for the rich but because that it is the way to stimulate the income we need to pay for this national programme of cohesion.”