Dean Lemire, left his Telford home to spend the Christmas holidays with his father Eric, in Arras. However, the UK went into lockdown on January 4 before Dean was due to return to his home in Oakengates, and it was decided that he should stay there until this week.
But his mother, Clair Chetwood, said that despite paying around £750 for the required Covid travel tests and replacement Shuttle tickets the pair were turned away by Border Agency officials in Calais on Monday morning amid confusion over the quarantine requirements.
However, the Home Office said the "regulations are clear" and in place to prevent the spread of the virus.
The plan was for Mr Lemire, 36, to accompany Dean on the Euro Tunnel vehicle carrier to Folkestone where he would hand his son to a relative at the Kent border before returning immediately to Calais.
Miss Chetwood said that as Mr Lemire would not be remaining on British soil he should not be forced to pay for a quarantine test kit at a cost of £210 which he would not be using.
A distraught Miss Chetwood, 36, said: "We did everything that was required, and followed the guidance to the letter.
"They both arrived at the border with negative tests which have now expired. They will need to do further tests before attempting to travel again.
"Eric was told he could not enter the UK without proof of purchase of the travel testing kit, and even though he will not be here to do the tests on day two and day eight, he would need to put my home address for the tests to be delivered and to say he will be isolating at my home. The border staff wouldn't let them board even though everyone else is saying he didn't need a kit as he'd got the negative tests.
"On the Gov.uk website, it says it is a criminal offence to use a false address on your passenger locator form, and if the tests are not swabbed and sent back to the lab, it carries fines of up to £2,000. It's criminal to break these laws and fill in false information.
"I am very worried we will get into trouble over these travel tests that can not be swabbed, or if the authorities come to my home to check that Eric is isolating here, when he will not even be in the country."
The Home Office stated: “The regulations are clear – all travellers arriving in the UK must take a Covid-19 test and get a negative result during the three days before travel into the UK. Every single check prevents the spread of coronavirus.
“If an individual feels they are facing a set of circumstances which is not covered by our published guidance, they can get in touch with the customer feedback team who will aim to offer further clarity on their situation.”
Telford MP Lucy Allan said: "My office is working with the family to see how we can help them navigate the restrictions and secure the safe return of Dean to the UK. It is understandably a very worrying time for them.
"The rules are complex and testing arrangements are expensive making it difficult for people to comply."