It is understood that Starmer and his family talked with the US pop star and her mother for around 10 minutes after he was invited to attend the Wembley gig on August 20, as first reported by The Sun newspaper.
It comes amid questions over UK government intervention in talks over the security for the concerts after Swift was given a taxpayer-funded police escort.
Earlier Downing Street had declined to confirm whether the prime minister met the singer at the sell-out show, but it is now understood that the meeting took place.
Keir Starmer's free tickets to Taylor Swift's concert in London were repaid earlier this month. (AP PHOTO)
The conversation centred around the Southport attack, and it is thought there was no discussion about security matters when they met.
Bebe King, six, Elsie Dot Stancombe, seven, and Alice da Silva Aguiar, nine, were killed and 10 others were hurt after an attacker entered a Taylor Swift-themed dance class in July.
The tickets to the gig came from Universal Music and they are among the items Starmer repaid earlier this month amid a row over freebies.
The prime minister announced he would cover the cost of around STG6000 ($A11,695) of gifts and hospitality he received since entering office following the donations backlash, as well as committing to changing ministerial hospitality arrangements to improve transparency.
Among the declarations he paid back were four tickets to see Swift at Wembley Stadium which were received on August 20 from UMG, the musician's record label.
It emerged last week that London Mayor Sadiq Khan and Home Secretary Yvette Cooper were involved in talks over security for the gigs after which Swift was granted a blue-light escort - a type of protection usually reserved for royalty and politicians.
Asked whether Number 10 could rule out Starmer having been given the tickets as a "thank you" after discussions between government and the force were followed by Swift getting security while in London, a spokesman said: "I completely reject that characterisation because it's ultimately up to the police to take operational decisions in relation to the security of these major events."
Downing Street has cited the terror threat faced by Swift in Vienna, which forced her to cancel gigs on the Austrian leg of her Eras tour, as one of the reasons the government was involved in security talks for her London shows.
Labour figures including Starmer, Khan and Cooper accepted free tickets to the concerts.
Number 10 and the Met have insisted that the police force is operationally independent and decisions on policing are based on an assessment of risk based on the individual circumstances of a case.
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