LONDON- Deliveries of Scottish seafood to Europe will not resume until January 18 after post-Brexit problems with health checks, IT-systems and customs documents caused a backlog, the industry's biggest logistics provider said on Wednesday.

Scottish fishermen have found themselves on the front line of Britain's new hard border with the European Union, with trailer loads of langoustine and monkfish being rejected by European buyers after they took too long to arrive.

Logistics group DFDS suspended its groupage export service - which allows multiple exporters to ship products in a single consignment - on Jan. 8 after the supply chain broke down under pressure.

It said on Wednesday it would resume delivery next Monday for a service which will now take longer. Goods picked up on Day 1 should now arrive for Day 3, at least a day longer than it used to take to send to France before Britain left the European Union.

"We are very thankful for the patience our customers have shown, knowing the painful situation the backlog has put them in," it said in a statement.

The company said the success of the resumed service would rely on IT services between DFDS and the authorities interacting properly and customers providing all the correct information for customs declarations. Health certificates have also taken hours to arrive, slowing down the export process.

(Reporting by Kate Holton. Editing by Andrew MacAskill) ((kate.holton@thomsonreuters.com; 0044 207 542 8560; Reuters Messaging: kate.holton.thomsonreuters.com@reuters.net))