She claimed the region has become a “bargaining chip” in trade talks between the bloc and the UK government.
Mrs Foster was responding to Assembly questions on the controversy around the UK government’s plan to override elements of the Northern Ireland Protocol through domestic legislation in the form of the Internal Market Bill.
She said her hope is the contention around the protocol can be removed with the striking of a comprehensive zero-tariff free trade agreement between the UK and EU.
The First Minister said she is “amazed” the UK/EU Joint Committee established to resolve outstanding issues around the operation of the protocol has not yet been able to iron out sticking points over state aid and at-risk goods.
Mrs Foster was asked specifically about a claim by UK chief negotiator Lord Frost that the EU has not provided guarantees it would give the UK approved “third country” status to allow it to move goods into the single market.
As Northern Ireland would effectively remain part of the single market for goods under the terms of the protocol, the UK government has claimed the EU is essentially threatening to blockade its goods from entering the region.
That contention has been rubbished by senior figures across the EU.
Speaking about the issue in the Assembly, Mrs Foster said: “The EU needs to stop using Northern Ireland to get their own way.
“We are not the plaything of the European Union and it causes great difficulties here in Northern Ireland when people use Northern Ireland in that fashion.”
She referenced Tánasite Leo Varadkar’s use of an old newspaper report of a terror attack on the border when he addressed EU colleagues during the height of the withdrawal negotiations in 2018.
“That was wrong as well,” she said.
Mrs Foster urged the EU/UK Joint Committee to make progress, expressing surprise there is still a standoff around the issue of goods being imported to Northern Ireland from Britain.
“I am amazed that that issue has not yet been solved because it’s a very straightforward issue,” she said.
Mrs Foster added: “That should not be used as a bargaining chip but instead it should be dealt with as quickly as possible.”
There needs to be an acknowledgement that east/west ... needs to be protected as much as having to deal with the north/south trade
On the UK Internal Market Bill, the First Minister said: “The GB market is our largest market so it is important that we have unfettered access into the market and that is what I hope this Bill will achieve.”
She added: “Sometimes when I listen to EU negotiators and they talk about peace in Northern Ireland, it is apparently only if we have free access north/south, there’s very little conversations about access east/west, and of course we do need that in a more fundamental way.
“I can understand why the north/south issue was such a big issue, and I recognise that, but there were other ways to deal with that.
“Those other ways were pooh-poohed and not listened to, and unfortunately we now find ourselves in this situation.
“So there needs to be an acknowledgement that east/west – the integrity of the United Kingdom – needs to be protected as much as having to deal with the north/south trade.”
During Assembly Question Time, Mrs Foster also discussed the volume of EU exit legislation set to pass through the devolved legislature in the coming months.
She said three primary legislation bills will be dealt with at the Assembly and eight at Westminster.