MONTREAL - The man who once headed Quebec's most powerful union is insisting he returned expensive gifts from an influential construction boss and paid for six-figure renovations to his own home himself.

Michel Arsenault, the ex-president of the Quebec Federation of Labour, is being scrutinized by the province's corruption inquiry over a cozy relationship between the union and former construction magnate Tony Accurso.

Arsenault began his fourth day on the witness stand by being grilled about expensive gifts and a nearly $100,000 home renovation done in 2009.

Wiretaps indicated that Accurso was prepared to offer some help for the renovations but Arsenault ended up paying for it himself after media reported on a trip by Arsenault on the construction boss' yacht.

Arsenault denied the media scrutiny had anything to do with him paying for the renovations and he says he has proof he paid for every penny of the work by using a second mortgage to finance the renovation.

Arsenault said that according to his recollections, the renovations cost $97,000 and he and his wife paid 100 per cent of the costs.