The Government is to review whether to legalise HIV home testing kits, which are currently banned in the UK.
While they are available to be bought over the internet, they are unregulated, often of poor quality and do not direct users to places where they can get support.
Former Tory health minister Lord Fowler, who chairs the House of Lords Health Select Committee, has called for the kits to be legalised.
He told Radio 4's You and Yours programme: "In this country we've got about 100,000 people with HIV, and we know that about a quarter of those don't know they are infected, and obviously that has profound public health impact because they can go on spreading the virus itself.
"So anything we can do to improve the testing position in this country I think should be done.
"When my select committee looked at it we took the view that this was one of the most important steps you could take because what it delivers is confidentiality."
Lord Fowler, who led campaigns to raise awareness of HIV and Aids during the 80s, said home testing kits would be more convenient for those who are worried they might be affected and get them diagnosed more quickly.
He added: "You can do it in your own home in your own time. As long as you go on to drugs at an early stage then you can live a long and successful and happy life, and that needs to be got over at the same time."
A survey by the Terrence Higgins Trust (THT) last year found that almost two-thirds of people would consider using HIV home testing kits if they were legally available and regulated.
Of the 490 people questioned who have not tested HIV-positive, 63% said they would consider using the kits if they were legalised and 51% thought legalisation would make them test more often.
Among gay men, one of the groups most at risk of HIV in the UK, 60% thought legalisation would make them test themselves more often.
In 2009, 22,200 people were estimated to be living with undiagnosed HIV in the UK.
A Department of Health spokeswoman said: "Currently HIV home testing kits are banned in the UK but we are reviewing this issue and will consult on it shortly.
"Confidential HIV testing is available free from NHS sexual health clinics."