The former minister said “inquests, inquiries and an independent commission creates a hierarchy of truth” and would cost “hundreds of millions for 15 years”.
“Painting the state as an aggressor, supporting our adversaries’ political objections and causing untold anguish for those that only ever deployed to protect us,” he added.
“We have neither the political capital nor the resources to spare for this unjust journey.”
Labour’s bill was introduced at Westminster last year following agreement on a joint framework with the Irish government.
The plans seek to replace the contentious 2023 Legacy Act, which included a ban on inquests and civil actions related to Troubles-era incidents.
The new plan involves a Legacy Commission to investigate Troubles-related killings, a separate information recovery body, and a dedicated legacy unit within An Garda Síochána (Irish police).
A package of protections for veterans has also been proposed by the UK government, but some MPs have said the measures do not go far enough.
Stormont’s First Minister Michelle O’Neill has previously accused the government of giving military veterans “preferential treatment” when dealing with the legacy of the Troubles.
The NIO last week said it had “listened closely to the concerns of armed forces associations”.
A spokesperson said the government would “shortly bring forward a substantial package of amendments to further bolster these protections”.
“Suggestions that veterans will be dragged through the courts are simply wrong,” they added.
“Our armed forces have always been bound by the rule of law, and those who served honourably and followed the rules have absolutely nothing to fear.”