Centrica, which owns British Gas, will take 25% of all power generated by British Energy (BE), once it is owned by EDF of France, the BBC has learnt.
The French energy firm will announce a Ј12bn deal to buy nuclear power firm British Energy on Wednesday.
As part of that deal, Centrica will take a quarter of all power generated by BE and a 25% stake in all new nuclear generators built by EDF.
The cost to Centrica of this investment will be around Ј3bn.
The deal with EDF is seen by Centrica as vital to reducing its growing dependence on imported gas.
EDF's acquisition of British Energy will be controversial, BBC business editor Robert Peston says, because it will be seen by some as handing the UK's nuclear future to a company owned by the French state.
Centrica's investment may placate some critics.
The involvement of Centrica also helped to persuade British Energy's recalcitrant shareholders to back the sale to EDF, since they are also holders of Centrica shares, our correspondent adds.
(BBC)
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