Proposed budget airline, Kiwijet, is denying suggestions it stole commercially sensitive information from Air New Zealand.

The low-cost carrier announced draft plans last week for domestic services in Dunedin, Invercargill, Christchurch, and Auckland, with a single fare structure.

But Air New Zealand claimed Kiwijet's plans were "remarkably similar" to their own plans for a low-cost airline, suggesting information may have been leaked.

Kiwijet have denied those claims and say they'll take legal action against Air New Zealand if the company continues to insinuate it stole plans.

Kiwijet are still considering a bid to buy JetConnect, which operates services in New Zealand under the Qantas banner.