Remaining in the customs union after Brexit would be a disaster, Labour’s trade spokesman said in the latest sign of the party’s divisions on the issue.

The shadow international trade secretary, Barry Gardiner, said remaining part of the customs arrangement would leave the UK bound by EU free-trade deals without achieving the benefits.

His comments came after Jeremy Corbyn said the party had yet to decide its position on future customs arrangements, while the shadow Brexit secretary, Sir Keir Starmer, has said membership of the customs union should remain on the table.

Gardiner also dismissed the idea of remaining in the single market under a Norwegian-style agreement, saying it would leave the UK like a “vassal state” – paying money to Brussels without any say over the rules.

He told BBC Radio 4’s Westminster Hour: “If you do what Norway does, what happens is the very reasons that most people who voted leave, voted to leave – namely to regain sovereignty, to regain control of our borders, not to pay money into the European budget – all are not achieved.

“To adopt the Norwegian situation would be to become a vassal state, because you actually end up paying money into the EU budget but you have less control over the regulations than you do now with a seat round the table.”

Corbyn said the UK must leave the single market as it is “inextricably” linked with EU membership – but the Labour leader indicated no decision had yet been reached on the customs union, saying “we haven’t jumped on either side of that fence”.

But Gardiner said: “I just want to point out the issues around the customs union, we leave the customs union because only member states of the European Union are members of the customs union.

“Other countries like Turkey have a separate customs union agreement, but the trouble with that is that it gives you an asymmetrical relationship with the third-party countries that the EU does a deal with.

“So the EU could do a deal with another country – let’s say America – which we would be bound by in the UK, we would have to accept the liberalisation of our markets, we would have to accept their goods coming into our markets on the terms agreed by Europe which could be prejudicial to us but we would not have the same access into America’s markets, we would be bound to try and negotiate it but why would America give us that access when it’s got all the liberalisation of our market that it wants. It’s a disaster.”