Speaking in Belfast after talks with the leaders of Northern Ireland, where post-Brexit trade rules have dominated politics for years, Starmer said his new government would first need to implement changes under the current agreement to build trust with the European Union, Reuters reported.
"We think we can get a better deal than the botched deal that Boris Johnson brought home and we will work on that," Starmer, who won a landslide victory last week, told reporters.
"We're not going to be able to get a better relationship unless we've demonstrated commitment to the relationship and the agreements that have already been put in place," he added.
Labour has ruled out rejoining the EU single market or customs union but has said it is possible to remove some trade barriers with the 27-nation bloc, which Britain left in 2020.
The largest pro-British party in Northern Ireland ended a boycott of the devolved assembly after tweaks to trading rules secured by former prime minister Rishi Sunak in February, but it has since called for more changes.
SD/PR