A boiler replacement company that bombarded the public with more than two million unwanted marketing calls has been fined £180,000.
Glasgow-based FEP Heatcare Ltd broke rules on phone messages after it became one of Britain's most complained about nuisance callers.
The company played householders a recorded message promoting its products and services without their consent.
Investigators from the Information Commissioner's Office (ICO) traced the calls to FEP Heatcare even though the messages did not identify the caller.
Ken Macdonald, ICO assistant commissioner for Scotland, said: "This company was already on our hit list.
"FEP Heatcare thought they could avoid detection by hiding their identity, but we tracked them down and have taken action."
The company came to the attention of the ICO in February last year when it appeared on a list compiled by the Telephone Preference Service (TPS) of the top 20 most complained about nuisance call companies.
Despite a warning it broke the rules again - this time by playing a recorded message.
These types of calls should only be made to people who have given the organisation their permission to receive them.
The ICO found that FEP instigated 2,692,217 unwanted automated calls between April and July 2015.
Mr Macdonald said: "We know people hate nuisance calls and what this company did made people angry enough to complain.
"The kind of calls FEP Heatcare was making - recorded and about energy services - generated the most complaints to the ICO in February this year. Combined with automated calls about PPI, they made up 66% of our recorded complaints."
One complainer to the ICO, who is disabled, said: "I don't very often get calls on my landline, so it means I have to get up and walk to the phone, which causes me inconvenience and pain - frustrating when it's a nuisance advertising call that I didn't want anyway."
Another said: "My husband has dementia and could agree to anything if I wasn't there to take the call."
As well as imposing a £180,000 fine, ICO has issued a notice to the firm demanding it does not make any further nuisance automated marketing calls.
Court action could follow if it fails to comply, it said.