In a speech on Monday, the Liberal Democrats spokesman on foreign affairs is expected to say that Mr Johnson will become more reliant on the US president if the Tories return to power next month.
Mr Umunna’s party is committing to spending extra money on defence and aid, claiming that the defence budget will be almost £1 billion more in 2024-25 under the Lib Dems than under the Tories.
The Lib Dems will commit to spending 2 per cent of GDP on defence, and will also maintain the current commitment to spend 0.7 per cent of GDP on International Aid.
The party said that thanks to the economic boost which they say will result from staying in the EU, this will mean they will outspend the Tories by £340 million in 2024-25.
In his speech in Watford, Mr Umunna is expected to say: “Not only will we cease to be that important bridge between the EU and the US but by withdrawing from the European Union, inevitably Johnson will become more reliant on Trump in the short term if he is re-elected.
“Johnson is desperate to secure a US trade deal to make up for the damage done to our global standing if Brexit happens.
“From my own contacts with the US Government, it is clear a high price will be demanded and close alignment with US rules and regulation demanded – we risk becoming a vassal state of the US if Boris Johnson gets a majority.
“Leave the EU and the UK under Johnson will become President Trump’s poodle. That is what is at stake at this election.”
Mr Umunna is expected to say Mr Johnson is “following the Trump playbook” and has become part of “this global network of populist, right wing, authoritarian nationalists”.
He will add: “Giving Johnson a majority is to give carte blanche to this type of politics in the UK – something which should worry us all.”