The government has been forced to publish documents that reveal how the disgraced former Conservative MP Owen Paterson directly lobbied a senior minister for a healthcare firm that was paying him to be a consultant.

Paterson contacted Matt Hancock, then health secretary, in the early stages of the Covid pandemic to promote Randox, a healthcare firm that paid him £100,000 a year.

Randox was awarded contracts worth nearly £500m during the pandemic without any other firms being given the opportunity to bid for them.

The new documents reveal that following Paterson’s lobbying, Hancock chased his officials, saying he was “very worried” about how his department was treating Randox and other firms.

Paterson told Hancock that he was “exasperated” that the government was slow to respond to Randox’s offer to help deal with the pandemic.

Amid regular contact between the two politicians via WhatsApp, Paterson also appeared, after an article in the Guardian, to ask Hancock to “kill once and for all” the suggestion that Randox had been awarded a contract because he was being paid by the firm. Hancock appeared to agree.

Labour MPs used a parliamentary motion to compel the government to publish documents. The Department of Health and Social Care had resisted disclosing documents relating to Randox amid criticism of cronyism.

Last November, Paterson resigned from the House of Commons after an official investigation found he had broken parliamentary rules when he lobbied for Randox and another firm. The investigation by the parliamentary standards commissioner had been started after an investigation by the Guardian into Paterson’s lobbying activities.

The documents were published by health secretary, Sajid Javid, who told parliament: “There are robust rules and processes in place to ensure that all contracts are awarded in line with procurement regulations and transparency guidelines … Ministers are not involved in the assessment and evaluation process for contracts.”

They show how Paterson contacted Hancock on 26 January 2020 highlighting the services that Randox could offer to combat Covid. Hancock responds swiftly asking Randox for more information about potential Covid tests.

On 25 February, as the pandemic began to take hold, Paterson complained to Hancock that it was “now 19 days since Public Health England (PHE) last contacted Randox at your request”. He added that kits to detect Covid were being shipped abroad, adding that “PHE’s attitude looks incomprehensible given current developments and time pressures”.

Five minutes later, Hancock responded to Paterson, saying: “Are you sure? I chased them again about it yesterday.”

Paterson complained that Randox had offered help to PHE, but added: “There was no sense of urgency … exasperating!” Hancock asked his officials for “chapter and verse” on how his department was dealing with commercial companies, adding: “I am very worried about this … if we are treating other companies like this we are failing.”

On 1 March 2020, an official told Hancock that Randox was one of the firms whose technology had been prioritised for testing by the health department.

Later that month, the Department of Health and Social Care awarded Randox a £133m contract to carry out Covid tests. It awarded the firm a second contract, worth £347m, in October 2020. Both contracts were given to the firm without other firms being given the opportunity to compete for them.

The government suspended the normal rules on holding open competitions for public sector contracts under emergency powers designed to speed up the process during the pandemic.

One civil servant raised concerns that the second contract had been awarded without competition, while another said the government was “paying dramatically over the odds”.

In October 2020, Paterson appeared to send Hancock a message saying the Guardian “yet again ran the story that you only gave Randox the testing contract because I am a paid consultant. If it comes up can you kill this once and for all I know absolutely nothing about the contract.” The answer, on WhatsApp, appeared to come back from Hancock: “of course”.

Paterson declared in his communications with the government that he was paid by Randox.

A Randox spokesperson said: “It is clear from these papers that Randox contracts were awarded in full compliance with government procedures and protocols in place at a time of the emerging pandemic.”

A spokesperson for Hancock said: “The extensive transparency publication proves Matt did nothing wrong. To suggest Matt should have ignored the UK’s biggest existing testing capacity because he was being contacted by Owen Paterson is absurd and would have been a dereliction of duty.”