The MP Andrew Bridgen has waded into an online row between his wife and the health minister Nadine Dorries over how the latter dealt with her coronavirus diagnosis.

Bridgen has a cold and a cough and claims he sat next to Dorries, who has been diagnosed with the illness, in a tearoom in Westminster.

Nevena Bridgen, an opera singer, claimed online on Friday morning that Dorries had jeopardised her family’s health by not mentioning him to Public Health England (PHE) staff who were tracing people with whom she had had contact before her diagnosis.

In response, Dorries said she had not been sitting anywhere near Bridgen but had advised him that if he was worried he should call 111.

Bridgen told the Guardian: “I can assure you that Nadine Dorries came and sat next to me at the end of my table. I wonder why she would now deny this?

“My wife is an opera singer; she really is a prima donna whereas Nadine only acts like a prima donna.”

Regarding his symptoms, the Tory backbencher said: “I don’t feel right. I am still waiting for a test. My 76-year-old mother-in-law [who lives with the family] is feeling all right at the moment.

“I am locking myself away at one end of the house, which is particularly upsetting when your 18-month-old son is crying for you. He is toddling and knows how to open doors. But I have to keep him locked out.”

After Dorries tweeted praise for the PHE contact tracers, Nevena Bridgen wrote: “Why did you not tell them that you sat next to my husband Andrew Bridgen on Thursday in a tearoom and that he can’t get the test now!

“I have the baby and a 75-year-old mother jeopardised. You were treated but no one is coming to help us!”

Dorries replied on Twitter: “Because I did not sit next to your husband. He was in the tearoom when I walked in, on another table not close to me.

“He texted me and told me he had sat next to me, I was too ill to discuss but not sick enough not to know, that wasn’t true. I told him if he was worried to call 111.”

Nevena Bridgen replied to Dorries, saying: “I’m sorry that you’re sick, I wish you to get well but let me tell you. You absolutely did sit next to my husband in the tearoom.”

The government advice for those showing mild symptoms changed on Thursday; people will no longer be tested and it is recommended they stay isolated at home.

Andrew Bridgen said after talking to 111 he was under the impression that he, his son and mother-in-law would be tested.

His wife had been in Belgrade, Serbia, having travelled there for a performance that was cancelled because of the coronavirus, and returned to the UK on Thursday. She charts her life on her Wives of Westminster blog, covering fashion, parenting and being a parliamentary “plus one”.

In response to someone who contacted her on Twitter, Nevena Bridgen said: “I guess if you are not a minister you do not get test nor help.”

Twitter users expressed dismay that the pair had argued on social media, with one writing: “We need to pull together in a global crisis.”

Andrew Bridgen told the Guardian on Thursday he believed parliament had been too slow to react to the virus, given that visitors entered the building from all over the world.

The international development secretary, Anne-Marie Trevelyan, has received a negative test result for coronavirus but is isolating at home, bringing the total number of MPs believed to be self-isolating to 11. Charles Walker, Edward Argar and Rachael Maskell are among those to have stopped face-to-face meetings, doing surgery work by phone.