Their demands are made amid a new analysis of test providers, which the party says shows "the spiralling prices" facing British travellers this summer.
According to Lib Dem research, of the 400-plus providers that meet government testing standards, 102 firms (24%) charge £200 or more, while only 47 offer tests for (11%) less than £50.
The most expensive test comes is currently priced at £575, offered by a provider in London.
In comparison, Greece and Italy have capped prices at £34 and £52 - while in France, tests are provided for free.
Most European countries have far lower prices than the UK – with a recent study by Abta and the Airport Operators Association claiming pre-departure PCR tests in the UK costing £128 compared to just £62 in eight European destinations.
The Lib Dems said the "disparity of prices" meant travellers faced paying over the odds and risked international travel becoming "a luxury" for only the wealthy in society.
Their calls come amid reports the UK’s competition watchdog, the Competition and Markets Authority, will look into PCR test fees and report back to health secretary Sajid Javid around firms using "exploitative behaviour" and "unfair practices".
The party’s spokesperson for health, Munira Wilson MP, said international travel “cannot become a luxury that only the wealthy can afford”.
“The price of PCR tests for international travel are a rip-off and far higher than most other countries. Many have not seen their loved ones abroad since the beginning of the pandemic and the cost of testing is a real barrier to travel," she said.
Wilson questioned why “when the cost of providing a test is estimated to be £20” a number of companies were charging travellers more than £100.
“Testing is vital in our fight against the pandemic but if it is safe to travel it should be affordable to travel.
“The Liberal Democrats are calling on the government to cap the cost of PCR tests for international travel, scrap the VAT on tests and cut the red tape that is keeping prices high.”
