Health Secretary Matt Hancock has said the public have a “new duty” to get tested if they have symptoms of coronavirus.
Mr Hancock's announcement came just a day after he exhorted those with symptoms that they “must” get tested, suggesting ministers are concerned the message is not getting through.
The government‘s track and trace scheme, designed to find anyone who has come in contacted with an infected person, finally got underway this week.
But its success depends on knowing who is infected and that requires those who fear they have symptoms to take a test.
Making a statement in the House of Commons, Mr Hancock said: "There's a new duty, and it is a duty that we now ask and expect of people.
"If you have symptoms - that's a fever, a new continuous cough, a change in your sense of taste or smell - if you have one of these symptoms you must get a test.
"We have more than enough capacity to provide a test for anyone who needs one and we have more than enough capacity to trace all your contacts."
Mr Hancock said that NHS test and trace was "working well", and that thousands of people had already been contacted and their contacts traced.
He also pledged to publish data on the programme.
But he suggested that would not be imminent, saying it was important ministers got the figures “right”.
Mr Hancock said the speed at which test results are returned had improved considerably in recent weeks.
Experts warn that delays in the receipt of positive test results will also affect how quickly ministers can trace an infected person's contacts.
Currently 83% of results from tests carried out at drive through centres are now returned within 24 hours, he told MPs.
Mr Hancock also insisted that ministers would not have sanctioned the re-opening of primary schools this week if they did not think it was safe.
He added that ministers wanted to increase the “detail” they receive on the R rate, the rate at which the disease spreads, in different parts of the UK.
And he defended the ‘two-metre’ rule for social distancing.
Several MPs including former environment secretary Theresa Villiers had called for the distance to be reduced one metre to bring it in line with some other countries' rules and to help the economy.
Mr Hancock said ministers had reviewed the scientific evidence behind the two-metre rule.
“The challenge is that the further apart you are, the less likely the transmission of the virus,” he told MPs.
He added that the government would "keep this under review", however.
He also faced criticism from Labour MPs over Dominic Cummings, the prime minister’s senior adviser, who remains in post despite apparent breaches of the lockdown rules.
Labour MP Chris Bryant said the feedback he had received from his constituents was one of "absolute fury. People think it is one rule for the government and their friends and one rule for everyone else”.