LONDON, April 17 (Reuters) - Czech billionaire Daniel Kretinsky has been exploring a possible bid for the owner of the UK's Royal Mail, which has seen its market value fall to 2.1 billion pounds , two people familiar with the matter told Reuters.

Kretinsky, the largest shareholder in Royal Mail's London-listed parent International Distributions Services (IDS), has been working with advisers informally in recent months to consider taking over the company, one of the people said.

Deliberations are in the early stages, the person said, cautioning there is no certainty Kretinsky will decide to go ahead with an offer.

Kretinsky holds a 27% stake in IDS via investment vehicle VESA Equity Invesment that he founded in 2018 with business partner Patrik Tkac, which also has a stake in J Sainsbury and Foot Locker, according to VESA's website.

VESA declined to comment.

IDS comprises two businesses, including international parcels network General Logistics Systems (GLS,) based in Amsterdam, and the Royal Mail business in the UK.

Royal Mail has faced hurdles over the last couple of years with strikes by postal workers, a cyber security incident, a fine from regulator Ofcom for missed delivery targets as well as losing a 360-year monopoly to deliver parcels from post office branches.

Any bid by Kretinsky for one of the world's oldest postal firms would follow a buying spree in Europe, including of indebted French supermarket group Casino last year, as well as attempts to buy half of Thyssenkrupp's steel business and Atos’s loss-making IT services unit.

The UK has seen an uptick in approaches for its London-listed companies, which have struggled with low valuations.

The Sunday Times in May 2023 reported that Kretinsky told the paper that he had no intention of bidding for Royal Mail and it was beneficial for the company to remain listed.

A deal could trigger an intervention from the British government under the terms of the National Security and Investment Act, which gives ministers a greater say over deals involving critical infrastructure.

The Department for Business, Energy and Industrial Strategy (BEIS) in 2022 reviewed VESA's plans to increase its about 22% stake in the company at the time to more than 25%.

Shares in IDS have fallen by two-thirds from its most recent peak of 571p in June 2021 to open at 213p on Wednesday.

IDS said revenues grew by 3.8% to 9.45 billion pounds for the 9 months ending in 2023, according its quarterly update in January. It expects to make an operating profit in the second half of this year that would offset the 169 million pound loss in the first half. ($1 = 0.8021 pounds) (Reporting by Amy-Jo Crowley, Emma-Victoria Farr and Marek Strzelecki. Additional reporting by Jan Lopatka. Editing by Anousha Sakoui)