Protesters gathered in dozens of locations around the country including London, Manchester, Glasgow, Birmingham, Brighton, Swansea, Bristol and Liverpool on Saturday, Xinhua news agency reported.
In London, crowds chanted outside the gates of Downing Street and waved homemade placards like "Resist the Parliament Shutdown" and "Defend Democracy".
Shadow chancellor John McDonnell called Johnson's decision to prorogue parliament an attempt "to shut down democracy".
"If Boris Johnson wants a mandate, then he should call a general election and put it to the people, " he said.
Queen Elizabeth II announced Wednesday she has given her consent to Johnson's request to suspend the British Parliament.
It means the House of Commons will sit only for a few days after it returns next Tuesday from its summer recess. Parliament will then resume with a State Opening of Parliament by the British monarch on Oct. 14, just over two weeks before Britain's planned departure from the European Union (EU) .
Critics of Johnson's strategy claimed that he has planned the suspension to give MPs as little time as possible to challenge his decision to bring Britain out of the European Union (EU) with or without a deal on Oct. 31. The leader of the opposition Labour Party Jeremy Corbyn has said next week is the "last chance" to stop a no-deal Brexit.
Further mass demonstrations are expected when MPs return to Westminster on Tuesday.
( With inputs from IANS )