Drivers of pre-2006 petrol and diesel cars now have to pay €11.21 a day to drive in London - on top of the congestion charge.
A senior figure in the Society of the Irish Motor Industry has warned that Ireland may become a dumping ground for such cars.
The move to try to get rid of London's oldest and most polluting cars was introduced by the mayor, Sadiq Khan.
Reuters reports that the £10 (€11.21) daily tax applies to diesel and petrol vehicles typically registered before 2006, which do not meet the so-called 'Euro 4' 2005 European directive, to regulate vehicle emissions.
The so-called T-charge will apply during the same 7am to 6pm weekday hours as the existing £11:50 congestion tax and could mean some owners paying a combined £21.50 a day to drive in central London.
"As mayor I am determined to take urgent action to help clean up London’s lethal air. The shameful scale of the public health crisis London faces, with thousands of premature deaths caused by air pollution, must be addressed," Mr Khan said in a statement.
"Today marks a major milestone in this journey with the introduction of the T-Charge to encourage motorists to ditch polluting, harmful vehicles."
The measures comes after Britain’s High Court ruled that UK government measures to combat air pollution were failing to comply with European Union rules on nitrogen dioxide limits.
The new measure is part of an 875 million pound effort by the mayor’s office to address air pollution in London, with the introduction of an Ultra Low Emission Zone (ULEZ) slated for 2019.
Nearly 9,500 Londoners die prematurely every year as a result of long-term exposure to air pollution, according to a 2015 study by researchers at King’s College London.
As I mentioned, a senior figure in the Society of the Irish Motor Industry has warned that Ireland may become a dumping ground for older and more polluting British cars.
Imports of second-hand cars have soared since the fall in the value of Sterling after the Brexit vote.
"A lot of people will think they will be getting a very good deal on these cars as they fall in value and become more attractive to Irish buyers.
"But that is just going to create a massive problem for us here unless the Government takes some action", he said.