FRANKFURT (Reuters) - Germany is likely in recession now as external demand is weak, consumers remain cautious and domestic investment is held back by high borrowing costs, the Bundesbank said in a regular monthly report on Monday about Europe's biggest economy.

Germany has struggled since Russia's 2022 invasion of Ukraine pushed up energy costs, and its vast, industry-heavy economy is now in its fourth straight quarter of zero or negative growth, weighing on all of the euro zone.

"There is still no recovery for the German economy," the Bundesbank said. "Output could decline again slightly in the first quarter of 2024. With the second consecutive decline in economic output, the German economy would be in a technical recession."

This weak performance has raised questions about the sustainability of the German economic model and critics argue that much of its energy-reliant heavy industry is now being priced out of international markets, warranting an economic transformation.

The government, however, has pushed back on gloomy projections, arguing that it is merely a perfect storm of high energy costs, weak Chinese demand and rapid inflation that temporarily holds back growth but does not fundamentally question economic strategy.

For now the weakness will persist, the Bundesbank argues.

Foreign industrial demand is trending down and the order backlog is dwindling.

Firms are also holding back investment, partly because financing costs have risen sharply since the European Central Bank pushed up interest rates to a record high to combat inflation, the central bank said.

High nominal wage growth is also impacting firms and strikes in key sectors, such as transport, could also weigh on growth in the quarter.

Disruption of shipping in the Red Sea will, however, not have a significant impact because there is plenty of spare capacity in shipping and because freight costs are only a minor part of the overall cost of goods, the Bundesbank said.

While the outlook is weak, the bank said it expects no major deterioration in the labour market, which has insulated the economy so far, and Germany was not facing a broad-based, prolonged recession.

"The weak phase in the German economy that has been ongoing since the beginning of the Russian war of aggression against Ukraine will thus continue," the bank added.