Neil Kinnock has said he was persuaded to accept a peerage so that he could help reform the House of Lords from within.
Mr Kinnock intends to use the Lords as a campaigning base
The former Labour leader and European Commissioner will return to Parliament when his tenure in Brussels ends.
Mr Kinnock spent the day his peerage was announced watching Cardiff City draw at home against Leicester.
Before the match began, he told BBC Wales the Lords themselves would have to vote for change.
Mr Kinnock, who has been less than enthusiastic about the upper chamber in the past, said: "I've had reservations about the House of Lords.
"The point was put to me very strongly that if we are to secure change, because there is a process of reform underway, then it's going to need people to vote for that change.
"That was one of the factors in my consideration."
Rhodri Morgan said Mr Kinnock could 'cherry-pick' issues to tackle
Mr Kinnock - who will take the title Lord Kinnock of Bedwellty, in reference to his first constituency - had already said he made his decision for "practical political reasons".
He intends to use it as a base for campaigning on national issues like "education, sustainable transport, industrial change and the ageing society" as well as global concerns like poverty and oppression.
Just a few days earlier, Mr Kinnock had promised he would campaign against further powers for the assembly in the near future should a referendum on the subject be called.
It could take him into opposition with long-time Labour colleague First Minister Rhodri Morgan, who said Mr Kinnock now had a "second opportunity" to take a role in Parliament.
"This isn't the way he'd have wanted to do it as an ex-European Commissioner - he would have preferred to be going into the House of Lords as ex-prime minister," Mr Morgan told BBC Wales.
"Nevertheless, you get this second wind, this second opportunity to campaign.
"[You can] cherry pick certain issues you really know you can make a difference on.
"Neil has already said what he's going to do."
Up in his home town of Tredegar, there was mixed reaction to the news.
One resident said: "I think he's a very nice man and he's done well."
But another commented: "I do think it's a bit of double standards, to say one thing and then do another.
"But then that's politicians for you."