"dependencies": {...},
  "devDependencies": {
    "less-stream": "~0.1.4"
  },
  ...

npm install --save-dev less-stream

var less = require('less-stream');

var less = require('less-stream'),
  fs = require('fs');
 
fs.createReadStream('path/to/less/src')
  .pipe(less())
  .pipe(fs.createWriteStream('path/to/css'));

var gulp = require('gulp'),
  less = require('less-stream'),  // gulp-less uses less.render() & can't support global/modify vars
  sourcemaps = require('gulp-sourcemaps');
 
// Basic compile
gulp.task('less', function () {
  return gulp.src('path/to/less/*.less')
    .pipe(less())
    .pipe(gulp.dest('path/to/css/'));
});
 
// With sourcemaps
gulp.task('less:sourcemap', function () {
  return gulp.src('path/to/less/*.less')
    .pipe(sourcemaps.init())
    .pipe(less())
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('path/to/css/'));
});

less(options)