Banco Santander to lay off 2,000 workers due to Popular integration -union

* Union wants Santander to reduce staff affected by layoffs

* Spanish banks have highest number of branches per person in EU (Adds details, and background)

By Jesús Aguado

MADRID, Nov 8 (Reuters) - Spain's biggest bank Banco Santander plans to lay off more than 2,000 employees due to the integration of Banco Popular, which it acquired in June after EU authorities ordered its rescue, a union said on Wednesday.

Santander, which took on more than 11,000 employees from Banco Popular, is expected to cut staff at both lenders' corporate centres to lower costs, its chief executive Jose Antonio Alvarez said last month.

The Comisiones Obreras union, one of Santander's largest, said it wanted the bank to find jobs for 575 of the employees at the company's other units.

A Santander spokesman declined to provide figures on Wednesday. Santander said on Friday it had begun negotiations with unions about integrating Popular (NasdaqGS: BPOP - news) 's headquarters.

When Santander acquired Banco Popular, it said it expected restructuring costs of around 1.3 billion euros ($1.5 billion)related to the deal.

In its third-quarter results last month, Santander took a 300-million-euro hit due to one-off restructuring costs but said it was not expecting further charges this year.

Like its Spanish competitors, Banco Santander (Amsterdam: 817651.AS - news) is struggling to lift earnings from loans in Spain as interest rates hover at historic lows, while increasing competition erodes margins.

As a result, Spanish banks have been trimming costs, including through branch closures, since a 2012 financial crisis which ate into earnings and pushed some into state bailouts.

Their profits have since recovered, but Spain still has the highest number of branches per person of any country in the European Union, according to recent data from the Bank of Spain.

Spain had 62 branches per 100,000 adults at the end of June 2017, data from the Bank of Spain showed.

Santander and Popular employ around 7,000 staff at its corporate centres in Madrid. ($1 = 0.8628 euros) (Reporting By Jesús Aguado; Editing by Angus Berwick and Louise Heavens)