The Swiss government says construction of a second tunnel on the main transalpine route is not a priority.
Amid increasing pressure by motorist associations and political parties to build a new tunnel through the Gotthard, the cabinet stood firm on its position.
The transport minister, Moritz Leuenberger, said on Wednesday there is no urgent need for another tunnel, because dramatic traffic jams on the main north-south route are limited to the main holiday seasons.
Leuenberger said a second tunnel would hamper plans to modernise the railway network. Such a tunnel would go against a clause in the constitution that prohibits the construction of new transit roads in the Alps, he added.
However, he did not rule out a second Gotthard tunnel at a later stage.
Hans Werder, a senior official at the transport ministry, told swissinfo that the construction of a second road tunnel would take more than 10 years.
"The current traffic problems at the Gotthard have to be solved now. We are working on refining the traffic management system", Werder said.
Instead the cabinet proposes upgrading the busiest stretches of the national motorway network, notably in suburban areas around the country's main cities.
The plans include building two additional lanes to the existing motorways between Zurich and the capital, Bern, and between Geneva and Lausanne.
In response, environmental organisations, including the Alpine Initiative, and trade unions welcomed the government's stance, but called for more investment in public transport on rail.
The main motoring association, TCS, said it took note of the government proposals but it would continue to lobby for a second tunnel at the Gotthard.
The government proposals will be discussed in parliament together with a people's initiative, which calls for a second Gotthard road tunnel and other measures on the main east-west motorway to ease the traffic flow.
Swiss voters will have the final word on both issues.
The country's main motorist associations last year collected enough signatures to force a nationwide vote on the issue. Parliament and three of the four political parties represented in the government have called for a second Gotthard tunnel.
Switzerland's existing motorway network covers about 1,900 kilometres and is due to be completed in 2015. The first stretches were built in 1962 around the capital, Bern, and on Lake Geneva in 1964.
by Urs Geiser